Cannot get into Win XP, lots of different errors, computer restarts and crashes...

Sounds like maybe your motherboard has a problem.  Check for a "popped" capacitor to any kind of discoloring.  "Funny smells" can indicate some kind of burning or melting.  If you burned up part of your HDD controller, you could get all kinds of problems ranging from driver errors (ntfs.sys) in windows to POST error codes or checksum errors.  Check your fans and check the voltages coming out of your power supply with a multimeter.  A multimeter should show +5 and +12 at the molex connector on your HDD.  (make sure the molex is plugged into the HDD when you check)  

I don't think replacing the CMOS battery will do anything for you.  If you want to replace something, your best bet is the motherboard.  

Best of Luck to you!

Sudden crashes that lead to nonwroking systems that can't be booted with a floppy point to:
- bad RAM
- bad power supply
- bad motherboard

The funny smell, if it was a burnt, electrical smell, is not good, it likely means a component failed, like a capacitor, as hartz21 suggested, and it could be in the motherboard or power supply.  Try swapping the power supply to test this.

Your BIOS checksum error could be a low CMOS battery or a failed motherboard.  Replacing the battery should be cheap and easy.

UPDATE!

After a bit of lunch i tried with the win xp CD again, it didn't work (crashed). All the fans are working fine. I switched it off and on again, this time the PC booted up for a few seconds-fans started up, and then powered down again. I switched it off, then on again,but this time i got nothing. I unplugged the pc, plugged back in and switched it on, the pc booted for a couple of seconds, before powering off again (by booted i mean fans started up-nothing appeared on screen).

It looks quite likely that its either the mb or the power supply, but i have no spare to test is with. Does what i've described  suggest one or the other at all?

There is a capacitor on the mobo that caught my eye- its at a funny angle, i.e. not pointing straight up... not sure if this is particularly relevant.

I wouldn't be too woried about a capacitor at an angle unless the leads underneath it are broken or it is getting in the way of something.  Caps can bend a little from side to side.  As far as PS or MB...it really could be either one.  If you can get the PS to spin the fans, check those voltages.  If they are bad (+5 should be +5 or more, not +4.99) then replace the PS.  If the PS is bad, then it may have burned up the MB and you'll end up replacing both.  If the PS has good voltages, then replace the MB.  Considering the errors you were getting in your first post, my guess is still the motherboard.

Unfortunately i can't get the fans to spin long enough to take a voltage reading, and i have disconnect everything i possibly can. The power supply seems supprisingly hot whilst the PC is not switched on.

I'm currently thinking that i will replace the motherboard and power supply - don't want to buy a new motherboard and have it blown by a faulty power supply! Does anyone know of some good socket A comparison charts on the internet (reasonably up to date)?

To stop XP from instantly restarting on a blue screen, do the following:

Right click "my computer", select properties
Click the 'settings' tab
Near the bottom under 'startup and recovery' click the 'settings' button
Near the middle of the new window, under 'system failure' uncheck 'Automatically Restart'.

Now the next time a blue screen occurs you'll be able to see what's happened.

Also, you might want to check your memory for problems. Firstly try removing one module and starting your PC, if it doesn't work try starting with the other one. If it now starts up with both, then go to this page:
http://oca.microsoft.com/en/windiag.asp

Click on the second link from the top "Download Windows Memory Diagnostic".

Download the little program and get a blank floppy disk. When you run the program it will create a bootable floppy disk with a memory testing program on. Switch off your computer and remove the second stick of memory. Start it up and boot from the floppy disk (you may have to change the boot order in the BIOS, but I'm sure you know what to do).

When the program loads it will immediately start checking your memory in 'standard mode'. Any errors encountered will be displayed at the bottom.
If your memory passes the test without any errors then it's probably okay, but just to be safe you can press 'T' which will make it go into a more thorough mode (this takes a bit longer - I recommend leaving it overnight to do this one).

After the standard test is finished you can switch your PC off, swap the memory modules and repeat the test to check the other one.

*note* any number of errors is a problem! If your computer returns one thing when it was expecting another it will cause it to crash.

I myself had a bad stick of memory several months back, I bought 1GB of TwinMOS memory (2 x 512mb) 'supposedly' suitable for an Athlon 64 environment. However my PC kept crashing when i did anything memory intensive, so I decided to check them both with the above program. One of the modules returned lots of errors (the other was fine) and I had to return them both to get a refund!


When troubleshooting things like this, it is often a good idea to remove the motherboard from the case and lay it on some cardboard. Remove and re-install/insert the CPU, Memory (just use one stick), Graphics card and ATX power connector (remove EVERYTHING else).
Connect the lead to the power button on the case, as well as a keyboard and monitor and try starting it up. If it works then gradually start re-building it inside your case bit by bit.

One more thing, how hot is your CPU heatsink? Is it hot to the touch? Did you install the heatsink yourself? Check to make sure it's making full contact with the CPU die.

p.s. I have an Enermax 465W PSU, it's never given me a second of trouble. So if you have to get a new PSU then I highly recommend it.

Hope this helps you out! :o)

Hi there, unfortunately the PC no longer boots (fans spin for 1 second then it powers down) so i cannot perform these tests, however it fails to boot whether either of the ram modules i have are installed on the motherboard. I'm now trying to find a suitable motherboard and power supply replacement....

Before purchasing a replacement, you might want to quickly see if it will boot out of the case as mentioned above, just to rule out shorting as a possible cause.

p.s. Does the CPU fan spin at all? Some motherboards refuse to startup if the CPU fan isn't spinning as a safeguard.

Try checking the connection from the power supply to your motherboard, if there is a funny smell it might be beacuse the pins were burnt out for some reason, i had this not long ago, check for burn marks on the actual power supply connector to the motherboard to see if this is the problem.

Anthony

Sorry for the slow reply, on inspection of the components, i unplugged the power supply from the motherboard, on several of the connection on the atx socket the plastic had gone black and melted on both the powersupply connection and motherboard. I went ahead and bought a new motherboard and a new power supply.

I have just put the components together, just the basics:
Motherboard
Powersupply
Hard disk
CPU (+fan)
Graphics Card

I realise that with such a big change in hardware, i shouldn't expect to get straight into windows, but the computer keeps rebooting as it enters windows (safe mode). It happens at the same point each time, as its loading mup.sys. Any ideas?

I also have a backup copy of win xp on a separate partition, when i tried to enter this i got the blue screen of death. It comes up with, STOP: 0x0000007B (0xFC46640, 0xC0000634, 0x00000000. 0x00000000).

HELP!

Actually, scratch this bit: "Alternatively, if you just go to setup XP as normal, and choose the same installation directory, it should install over itself as well."
If I remember right, the only option is to repair XP. Maybe I was thinking of old '98

p.s. What make is the new motherboard and power supply? Also, what graphics card do you have?

I think its working... did as suggested and did an install-repair, things seem ok, I hope! I'll leave the question open for a couple of days just in case.

Thanks for all the help!

p.s. although a bit irrelevant now, i bought a thermal silent pure power 480W (its not very silent, but very good quality, couldnt get hold of an enermax in a short time scale) and an Asus A7N8X-E Deluxe; was a bit sad to see the ultra ata raid gone (it has sata raid instead), but its difficult to get ultra ata raid nowadays. Fingers crossed it all will stay working...