My computer keeps rebooting at startup

Does the machine allow you to start in  safe mode?

If so you may be able to run a av scan from there

Other wise to rule out the virus issue remove the disk attach to another machine with a working av package and scan the disk from there.
 

ok, I started the system in safe mode, and I'm actually doing a full scan with CA Anti-Virus, it sould take hours !

I had already disconnected the internet cable and used the shutdown -a to prevent the computer to shut down after 60 seconds.

The update listed on PC Hell is older than the one I have on my system, so I tried it and it didn't work.

I also ran a quick scan of "microsoft malicious software removal tool", July 2008 version, it says that I have no infection...

I'll stand after the scan, and if needed, I'll try with Symantic removal tool (if I'm able to install it on my machine...).  Tell me if you get other ideas, cause I'm not convinced that a simple scan will do the job.

Thanks

The problem could be this virus:

W32/Spybot.worm.gen.p
http://vil.nai.com/vil/content/v_135336.htm

http://techrepublic.com.com/5208-6230-0.html?forumID=49&threadID=162758&messageID=1672215

I have been running CA Anti-virus for about 5 hours from now, and also ran a full scan of MS Malicious software removal tool, NO VIRUS found by now!!  My disk C has been totally scanned, the time remaining is for Disk E, witch not contains Windows XP, only data, so I'm not sure if the virus could be founded there.

I also ran a scan of Symantec, NO VIRUS found ...

I'm starting to think that maybe it's not a virus ?!

Thanks

My CA Anti-virus and MS Malicisous Software Removal Tool scans are complete and absolutely no virus has been found.  I have the last version of my anti-virus software and it was updated yesterday before the problems happened.  So it seems my problem is not caused by a virus.  
My internet cable is still unplugged.

Here are additionnals symptoms I get;  when my computer starts up, after login in, the desktop (with wallpaper) is displaying, but nothing else is showing, if I connect and disconnect my USB key, icons are instantly showing up, programs configured to open at startup opens but they all crash one after the others.  The bar at the bottom don't display any programs aliasses no more and I lost my "Start" menu at the left.  My Anti-virus is on, but with a big X, so it's disabled.  I cannot copy documents from a disk to another.

After, I keep gettng the count down before the shutdown...

Any idea what it could be ?

If the system runs ok ish in safe mode try going into msconfig  >start>run> msconfig and click on the services tab select "hide all microsft services" button then disable all, on the startup button just click the disable all.

Resatrt the machine see if the lsass issue returns. (hopefully not) then select a couple of items,first in services then start until it returns.

Once you find what is causing the problem report back here and we try to help.

Hi WallD,

Same problems happens with all services disabled...

Do you think that it could be a better idea to reinstall Windows XP ?
... I saw on my Windows XP disc, a repair tool, is this tool could possibly solve the problem ?

thanks

I forgot to mention, I also had an error when trying to go to System infos :

"RPC server unavailable"

maybe it could help to know that ...

sometimes I'm getting this message when trying to log in

"The system cannot log you in due to the following error, the handler is invalid"

Reformatting your computer would indeed solve your problem, at the end it depends on how much time you want to spend on this issue.

just to let you know, I reformated my PC :)

thanks a lot !