What is causing computer to lock up intermittently

First culprit could be something like your anti-virus software.  Wouldn't hurt to disable that to see if affects system performance.

You could also have some type of malware interfering with your system.  I would recommend scans with SpyBot, Malwarebytes

Something that might help clue what is going on is once you encounter the hour glass, try to get to the Windows Task Manager (CTRL-ALT-DEL), get to the Performance tab to see visually if you notice a spike in CPU utilization.  

If so, try to get the hourglass to repeat itself, and go to the Process tab, rank the processes in descending order by the CPU column, notice for anything significant 25%, 50%, 75% or better.  I'd say anything less than 10% is likely negligible.

Thanks for responding DJ. I have run Spybot, Ad-Aware, I also run Super Anti-Spyware and have removed what they found. Unfortunately, when this lock up occurs, the keyboard immediately stops working. So unless I pull up the task manager as soon as I log on that wouldn't help.

Here is the hijackthis file.
022609.txt

Link to UBCD:   http://www.ultimatebootcd.com/

Could be a Windows problem:

Run System File Checker to restore and repair all Windows files:
Start » Run » Type "sfc /scannow" without the quotes. There's a space before the /.
Click OK.
Have your Windows CD ready to insert if prompted when repair is necessary.

It could be many things and as Wilcomp and Vallis said above, I would suggest to open the computer case and check for bad cap: http://www.badcaps.net/pages.php?vid=5
And also see inside if there is a lot of dust formed ....

Hi All,
Added a couple .dll files with sfc. No errors on hard disks, so far. Only did quick tests though. Will run Memtest 86+ overnight.

If none of the above results any errors or things that indicate problems then I would try and remove any hardware you dont need and see how you get on and maybe get a replacement power supply as a last resort - maybe a re install.

For the time being it seems to have stopped. I'm getting ready to do some video work I'll see how it responds during that time. I relay any pertinent information.

no problem :) hope the above helps :)

If you really don't want to do a reinstall, a Repair installation of Windows may be a second-to-last resort.

:-)

This leaves all your programs and data intact while reinstalling Windows.

1.  Boot the computer from your XP CD (if this won't boot, you may need to change the order of boot devices in BIOS setup).
2   Eventually you will see the "Welcome To Setup" screen. Press the Enter key to start Windows Setup.
3.  Be careful NOT to choose R, which is "To repair a Windows XP installation using the Recovery Console".
4.  Accept the License Agreement.
5.  Windows setup will search for existing Windows installations.
6.  Select the XP installation you want to repair (there is usually only one) and now press R to start the repair.

More complete instructions on how to do this, complete with pictures, are here:
http://www.michaelstevenstech.com/XPrepairinstall.htm

Before doing that, or a clean install as gecko_au2003 suggests, I recommend spending a few $s on imaging software. That will save future similar pain. See here:

http://mywitsend.co.nz/computer-stuff/software/15

Wouldn't be without it.

Thanks to all. It hasn't happened in the last few days, so I don't really know who to ascribe the points to. I hate when the problem just seems to correct itself. Everyone is so helpful.

Thanks for the information - any chance you could go through event viewer ( control panel --> administrative tools --> event viewer )

And post any errors back here that relate to VLC player ?

Also was that the latest version of VLC player ?