Several things here :
1. If you want to eliminate the memory as the problem, download memtest86 or similar & check the RAM http://www.memtest86.com/
2. Go into device manager & check for any IRQ conflicts or other problems. Pay particular attention to the USB devices
3. If you get the IRQ_NOT_LESS.... error again, can you tell us the rest of the info i.e. You will see a line that reads STOP 0x0000.....
Can you tell us everything on that line following the word STOP.
Also, note if there is a device driver or system file listed under it (such USBPORT.SYS..... for example)