Computer Freezes

I have had my computer since 2009. I'm running Vista home premium 64bit. In the past week it started to freeze up shortly after startup. I have done a system restore to a previous configuration that I know worked from about a month ago. I have ran ms security essentials full scan and found nothing. I have changed the msconfig startup to the diag setting to eliminate any unnecessary programs in the startup process. Nothing I have done seems to help and I am stumped.

Welcome
Lets see how it works in safe mode
Download and make a full updated scan with malwarebytes
Follow the clean boot procedure (although probably similar to what you did, we cannot take a chance to rule out the true cause)
http://support.microsoft.com/kb/929135
Report back

Possible causes
Check memory with memtest86
Make sure that you are not over heating.
Try in safe mode; report back if it works properly.
Try a clean boot
Make sure PSU is working properly
If overclocking, restore to original
Test hard drive at company website.

Check back and I will get you some links that you can use for the above
http://www.geekstogo.com/forum/topic...ing-memtest86/
http://support.microsoft.com/kb/929135
http://malwarebytes.org/
http://www.almico.com/speedfan.php

Me Bad!
Almost forgot. Type event viewer, in search (by start button) and look for errors that may show the cause of the problem.
Go into event viewer and look for critical errors relating to the problem

You want to look for critical errors (they have red in the left column ).
When you find them you want to look for critical errors that say app hang, app crash, or anything that relates to the problem.

This seems like a lot, but go slow, ask questiions and you will be up and running

I haven't gone through all of your procedures yet but heres an update. I can run in safe mode no problem. After going through process of elimination I have found that I can leave all the start up applications on and disable all the startup services it will not freeze. After restarting with those settings the only service that still runs is Group Policy Client. I have noticed while watching the memory usage that it hovers around 1.5gb to 1.9gb but freezes when the usage goes over 2.2gb. I have 8gbs of memory on my system. Let me know if that sounds suspicious. Can you see my system specs that I've made.
thanks for your help.

If that were me, I would take memtest.
Guide to using Memtest86+ - Geeks to Go Forums
Rule out memory problems.

OK I ran the memtest86 and they all passed. I also updated my chipset to the latest version. It was way out of date. I am still having the same issue. I will try the malware process next. Are there any really good free programs I should look for?
Thanks again

I have list of free software that will keep you busy forever, but for now lets get this fixed.
YOu did not pass the Memory test. It is an overnight test that will take a minimum of 8 hours to do correctly. Read the instruction, again.

On the memtest how many passes do I need to do on each stick? I ran one pass each so far and had no errors. Each run took about 20 min each per stick so it did take over an hour. I have also ran a full scan using Malwarebytes in safe mode with the updates and found nothing there either.

Mem test 8 passes
If failed 8 passes in each slot with a good stick
If passes 4 pases in each slot with a good stick

Memory seems the most likely, if it is not memory, we can move on.

Just wanted to say, if it's not an overheating problem, uninstall WinPatrol if you have installed it. I had a freezing problem that lasted over a month and stopped when I ditched that program. Also, running "sfc /scannow" in command prompt (without the quotes) as an administrator might help.

If it is WinPatrol, it will show up with the clean boot procedure that has been suggested.
Make sure that you untick that one too.

It may be a memory leak caused by buggy drivers or software. Have you installed any new software that may have caused the stalling.