Hi, I have a peculiar problem with my system. I have a MSI motherboard (nforce2 chipset) with an AMD processor (XP 2400+). I had it running with 1 GB RAM (2 X 256 MB @ 266Mhz + 1 x 512MB @ 333Mhz) until 2 days ago when there was a RAM failure. One of the 256 MB RAM chips had conked out. The remaining 2 are fine (tested on another system). The strange thing is that now XP refuses to boot with more than 256 MB RAM. It bugchecks with IRQL_NOT_LESS_OR_EQUAL and similar. I also have Windows 98 on my system which boots without any problem. I ran the windows memory diagnostic tool which crashes on testing any RAM greater than 256 MB (tried all varieties at the repair shop 266-400 MHz, 512-1024 MB). Even with 256 MB RAM XP crashes if I start too many programs. I suspect its a motherboard problem. I tried tinkering with all BIOS settings without success. Last night XP wouldn't boot even with 256 MB RAM. Then I had to reduce FSB to 100Mhz from 133MHz to make it start. Can somebody please suggest how to resolve this, or atleast find out if it's a hw or sw problem? Any help will be greatly appreciated. I'm attaching the last three minidumps. Thanks in Advance..