I've just replaced the 6gb hard disk on my brother's 6 year old computer with a 120gb one(my old one). I seem to have connected everything fine, but when i switch the pc on it does not boot.The fans work and there is power anough to keep it on but it wont do anything apart from that. When i had tried replacing the hard disk 6 months ago, the same thing had happened but when i reinstalled the 6gb one, the pc booted fine.

Your MOBO may not be able recognize a 120GB HDD.

I just got thru working on an older pc, a '97, 200 MHz. I replaced the 4gig with an 80gig and had some similar diffaculty. Did you set the jumper on the HDD to Master? Do you get any screen at all on your monitor or is it totally black? Can you get into the BIOS setup? If you can, you can find out if the HDD is even being detected and the max volume it is detecting. In my case, out of the 80gigs, only 8 1/2 were detected as is the case with older pc's and MB's.

There may be a BIOS update for your MOBO (unlikely), the HDD manufacturer may have an overlay program (common) or you can use a PCI/IDE adapter card if your MOBO has PCI slots and one is open.

Webdezinerz, I am not getting at screen at all..its just black (ie I cannot get into bios).So the maximum it can take is 8 1/2 gb? In that case ill just re install the old 6gb hard disk. Thanks for your support!!

No problem Reverend, There are a few other things you could try also. If all you are getting is a black screen, make sure the IDE cable is properly attached to the MOBO and that the HDD is attached to the other end of the cable, Not the middle connector. Also check to see if the Ram is seated properly, if you have more then one stick installed, try taking one out at a time and booting up the machine. If still nothing, another option you could try is resetting the BIOS. Sometimes when making a hardware change in an old pc, as with what you are trying, they don't take well. Look for the CMOS battery on the MOBO, (make sure pc is Unplugged) it will be a round lithium battery approx. the size of a coin, pop it out and wait about 10 min. then place it back in, then boot up the machine. If still no go, find the CMOS reset jumper on the MOBO, it is usually a small black or blue jumper with (3) post exaxtly like on a HDD. Sometimes it is located near the battery. with you pc Plugged into the wall but NOT turned on, move the jumper over to cover the other post, wait about 10 seconds and move it back, then boot up your machine. This will reset everything back to factory defaults and hopefully one of thease methods will help you out. And as Badboy stated, if you are going to try and use the 120gig, find a PCI/IDE adapter card if your MOBO has PCI slots and there one is open. Good Luck.

Thanks, will try as soon as i have the chance! Thanks Guys!