I am hoping some of you more knowledgeable guys can make some sense of this because it has me scratching my head. I have been working on a pc today that would not boot up because of an "Invalid system disk" error message, i ran chkdsk /r from the windows XP disk and rebooted the machine for it to load into windows, except it wanted to activate windows first. Why I can't explain as all I had done was run chkdsk, I reloaded all the software a couple of months ago and had activated windows at the same time.Since the reboot a few weeks ago it was running fine and then a couple of days ago it threw up the "invalid system disk" error. Once windows was activated I rebooted the pc and again the "invalid system disk" appeared but I found that if I left the Xp disk in the cd-rom it would happily boot into windows. Without the disk the error message appears, with the disk it boots up OK. Once it has booted into windows I have noticed some strange things happening, the graphics card shows an error in device manager because it can't start, its a geforce MX400 card so windows has its own drivers for it. Also it won't access the internet. the network icon tells me its connected but when I check ip address it does not have one, if I click on the repair button it says it can't repair it. I have tried ipconfig but it just throws up error messages about being unable to find the address. I am wondering if it needs another reboot but twice in as many months suggests a problem somewhere. Apart from the above problems it appears to be running OK, the machine is a few years old with an Athlon 800 processor and 384MB sdram, 40gb hard drive. I am hoping some of you guys can shed some light as to what the heck is going on here.