I have an HP Pavilion 6635 with a PC100 and a single memory strip of 128Mb of RAM and am trying to increase it with a second strip of 128Mb. When I try to repower I get an error loading windows statingSystem32\Drivers\PCI.sys is missing or corrupt and suggests using ther original XP disc to repair and select "r" at the first screen. If I try to do that, I don't get a screen allowing me to select "r", it automatically inspects the system configuration in the Windows Setup with a Blue screen and comes back with an immediate error of "Unexpected error (267385611) at Line 1768 d:\xpclient\base\boot\setup\arcdisp.c. If I remove the new memory the system starts just fine. Maximum for this computer is 256Mb of RAM and the system recognizes it OK. System Setup shows Block 0 = 128Mb and Block 1 = 128Mb and the Cache is 128Mb. I was told I needed an extra version of the PCI.sys driver to recognize the memory but can't locate it in the Downloads database and I have also exchanged the memory and still get the same issue. Can anyone help?