Weird Crashing Error - Maybe Mobo? Please Read.?

Hello. I am fixing my brother-in-law's computer that my OTHER brother-in-law built with all kinds of stupid hacked beta versions of windows, etc...

- I did a clean install of a legit Windows 2K on a new harddrive.

- Because I didn't make the computer, I dont know what kind of MOBO it is. It has an onboard ethernet connection. I couldn't get it to work, so I put in a PCI ethernet card and installed the drivers and I am able to connect online

- Computer is running a GeForce FX 5700 LE video card. I DL'd the drivers, installed it.

- I downloaded and installed Firefox.

- DL'd Avast! Antivirus and ran it, did a boot scan, etc... no problems.

- I did this whole process TWICE to rule out a bad install of the OS

When I open up IE or Firefox and resize the window or attempt to generally move around, SOMETIMES it will throw an iexplorer.exe error. Sometimes it will simply crash the computer all together and force it to restart. All fans are working.

Suggestions? Or is it a lost cause?

Weird Crashing Error - Maybe Mobo? Please Read.?avast

probably a weak power supply....that or the ram is bad....

If you have an extra ram module you can pop in there to rule out ram, that will help narrow the search....

Weird Crashing Error - Maybe Mobo? Please Read.?ducati

Why don't you download a free program that tells you ALL the info about your computer? Here's that link. http://search.yahoo.com/search?p=belarc+... I find it extremely helpful in situations such as yours.
As you mentioned that the mobo had an integrated ethernet connection and above that you installed a PCI ethernet card that might be the reason try disabling the onboard ethernet connection by going to BIOS and disabling it...bcoz it seems that it is not disabled and causing a conflict...Try this out..