XP crashes rendering from both 3d studio max 6 and vegas video 5b; works on W2K

Firstly, try disabling virtual memory - there may be an error on the hard disk at some point which is being used as VRAM, that could be causing the problem.  You might find you run out of memory when rendering but hopefully that should give you a message.  You should also check the hard drive for errors with scandisk or another utility you might have.

Next I would suggest checking the temperature of your computer, as this is a fairly common problem now when the computer is under heavy load and could also explain the games restarting as well.  I had this problem myself where my old PC used to restart while playing Warcraft 3.  The easiest way to check is to go into the bios and check the CPU temperature from there when the PC restarts itself.  Also you might want to put an alarm on that tells you when the temperature goes over 70 degrees.

Im guessing you've already updated OpenGL and DirectX to the latest versions.
Try the above suggestions and get back to me, something else I'd like to know if has this been happening every since you've tried these things or did they used to work fine at some point and have started to crash recently?

The games probably always worked ( might have crashed once or twice but not consistintly).  I just started using 3d stuido max 6 (upgraded from 3.1).  I dont think 3.1 ever crashed, but we did not use 3.1 very much on this computer since the computer is only a few months old.  Vegas Video was just upgraded to the network version so I never saw the problem with Vegas Video.  It is very reproducable; games, vegas and 3d max all crash it.

 I will check the things you have suggested.

I disagree, the question asker had not replied to the suggestions made in my comment, but has suggest he will try them but has abandoned the question after this, therefore there is a good chance that my comments helped to provide a solution.

I have not had time to check disable the virtual memory and to upgrade openGL and DX.  My Bios does not show a temperature; I did check this.  Is there some kind of software that will let me check teh temperature while the computer is booted?

I tried a mother board monitor program and am rendering now.

It says:

Case temp 96F
Chipset Temp 105F
CPU Temp:  131F

At what point should I get worried?

I upgraded Dx today and I am still running the crash tests I have been using..  I check my OpenGL; its current.  I am going to pull the computer out of the cabinet its in and try your idea to blow a fan and see what happens.   I will let you know.

I also used TuffTest Pro and all those tests worked.  I did not run it for hours or anything like that.  But it tested my memory, video and drive and they all checked out fijne.

I will try your stress test program recommendation too.

I disabled paging (set my page file size to 0), and it still crashes.  I have a particular render I do.  Once it rendered all the way through when I did not save to disk.  Then I turned on save to disk, and it crashed.  The temperature was lower than I said above so I dont think it was the temperature this time becasue it went much longer before.  This is pretty quick.  So I then turned off my page file, and rendered the same and it crashed again.  So now I dont think its the page file either.  On this second crash, I was not saving to disk and I was not paging.  It just crashes after about 25 frames.  Once it did not, but usually it crashes with this file.  

I could try the stress test, but that might not do much good since I can crash it easily without my own stress test.  I will next try openign it up wiht a fan and see what happens.