A couple of months ago my brother's kids' computer started giving the message "Invalid System disk, replace disk and press any key to continue". After a few times of that it just wouldn't boot at all ... no beep, no nothing. I brought it in to work with me and ended up replacing the mobo, CPU and case as it was a P2 and I couldn't find a mobo that would fit the CPU and case. I brought my brother's PC in with the idea of him getting the new parts and transferring all his other stuff over to the new unit and then moving the kids' stuff all over to my brother's old unit which was a Cel 500 / 128MB. I got the 500 with the kids' hd in it to boot with a boot disk and started a format at which point I got a message saying "Bad sectors, disk unusable". I took out the boot disk and tried to boot normally but same as their old machine ... nothing at all. I tried swapping out everything I could and still nothing ... no beep ... no nothing. I hooked the hd up to another machine as a secondary just to see what was on it and to try a virus scan. The disk was packed full and trying to virus scan it ... completed in two seconds and saying no virus. I've replaced the hd and mobo in the Cel 500 now, got it to boot up, format and loading WinME on it but I am stumped as to what would fill that hd up and kill the mobo that fast. Any ideas or input would be greatly appreciated. Thanks MindsEye

Sorry ... I'd just like to add that as far as we know, as long as my brother has had this machine it has never been hooked up to the internet.

Are you sure your power is good ... seems you must be frying the motherboard ???

this is a huge problem alot of people have. What happened was your root directory was removed or corrupted. Reformat is so far the only fixing of this. It is NOT a virus.

hylian lynk - thank you for your reply. No problem with the power at all. I work for a software development and networking company so boss has made sure we have stable power supply. As for the 2 PC's that blew ... kind of hard to believe that the same thing happened to both power supplies within a couple of days of each other. Also the fact that each work great once I replaced mobo and hard drive. But thank you for your input. renxwar - thank you too but I am wondering how to format if I can't get the machine to boot from a floppy or otherwise? We tried the hard drive in a different machine as a slave and still no go. Thanks for your input. MindsEye

Hello all, I am having the same problem, "Invalid system disk etc etc. It is a home made machine with everything built into the mobo. Was running win 98se. Everything was working fine, except slways needed to boot from floppy. Yesteday the error message came up. It won't even test the A drive on start up. so I copied the boot disk info to cd and went into bios and changed it to boot from cd, it tries but then goes back to the Invalid... Thing is I cannot reformat because I can't get a prompt of any kind. Do I need to replace the mother board? I don't want to try out any of the parts in my good computer for fear of trashing it too. I am not really educated in computer lingo so if your reply make it simple if you can. any suggstions would help thanks

Hi gazza I first replaced the motherboard and got the machine to boot once with a boot disk. After that ... no more. I once more replaced the motherboard and the hard drive and then everything was fine and still is. This is why I am wondering if it wasn't a virus that somehow corrupted the bios on the motherboard on that one boot. Oh well ... I would recommend replacing both the motherboard and the hard drive. I'd hate to see you have to go thru what I went thru. HTH