DRIVER_IRQL_NOT_LESS_OR_EQUAL

See this: http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/Default.asp?url=/resources/documentation/Windows/XP/all/reskit/en-us/prmd_stp_ottj.asp

This: http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/Default.asp?url=/resources/documentation/Windows/XP/all/reskit/en-us/prmd_stp_hyzf.asp

and this: http://www.tek-tips.com/gviewthread.cfm/lev2/67/lev3/70/pid/779/qid/308429

The instructions for resolving these issues are not necessarily any less complex than the technology with which you're working, so "simple" is not necessarily an option, but you may want to be aware of the fact that you're well past the "return for refund" point for sending the system back, so it will most likely be to your advantage to start getting acquainted with basic troubleshooting and resolution steps for the system.  You're probably experiencing a driver conflict, and those are often rather easy to rectify.  You might also want to review the onboard Help and Support (Start - Help and Support) material for "System Restore," as outside of rolling back the bad driver, that is frequently the quickest way to get problems like this fixed.

I had a similar problem after Dell replaced the motherboard on my Latitude CPxj 650.  Before the replacement, I had 256 MB of memory with both slots used by 2 128 MB modules.   After  the replacement only 128 MB module in slot A worked.   Any time I installed another memory module in slot B, I would get a DRIVER_IRQL_NOT_LESS_OR_EQUAL error or other BSOD's relating to memory.  I knew it wasn't the module because I tried known good ones from co-workers' machines and the motherboard was new.  I even swapped the CPU board and I still got the same error.  Finally, pressing down on the memory module did the trick.  The two memory sockets are from different vendors.  Slot A is from Foxconn  and slot B has no name.  It seems that whoever made the motherboard ran out of Foxconn sockets and substituted something that doesn't make good contact with the standard memory module.  To fix the problem without having to permanently press down on the memory module with my finger, I put some weatherstripping foam between the cover and the module.  I haven't had a problem since then.