I've found helpful info from this site in the past, so I thought I would register and run this problem past you guys.
First, before I start. FORMATTING THE DRIVE IS NOT AN OPTION. It is filled with 250 gigs of irreplaceable backups and data.
Now, the problem:
Last week, my desktop died, reboot looping and the whole works. tried many things, eventually ending in a reformat and reinstall of XP on my primary hard drive. This fixed the problem as far as making the machine work. but when i hooked my 300 gig SATA secondary hard drive back in, it shows as drive E, and unformatted (every time i try to open it it asks if i want to format... NOOO!). and disk management shows it as 128 gb. (bios sees it as 300 gb still)
Now, I know i used to be able to swap hard drives around in windows 98 with no problems, but this is the first time the issue has ever really come up with XP (the issue of accessing old data on a new install of XP). I know it should be possible, i just cant figure out how. Is there some registry trick to make it stop trying to format? or should I reinstall XP with the SATA drive hooked up? (i'll go try that now just for kicks...)
Please help if you know a way to do it without reformatting. if i lose this data i'll be reformatting myself too with a bullet to the head.
Have you upgraded your Windows XP installation to at least SP1 yet? XP RTM (i.e. no service packs) cannot recognize IDE/SATA disks larger than 137GB/127GiB.
If this is the case, remove the 300GB drive and install at least SP1 to your primary installation (SP2 with all updates or SP3 preferred). After that, plug the 300GB drive back in and see if your partition is now recognized.
I'm sure SomeJoe7777 is right. You had to re-install XP, and it's likely it was not the latest version on the install disk. That 128 GB number is a big clue - that is the max HDD size the OS can deal with until you upgrade to SP1 or later to add what's called "48-bit LBA Support".