hi, i try to do a fresh reinstall with xp pro pre sp1 on my broken pro xp sp3 partition. (broken meaning my windows is slugigsh and plagued with all kind of ****). Now when i boot with the install cd, it did not recognize the current ntfs partition that has the broken windows on. It give me the only option to format it to ntfs. Problem is i dont want to lose everthyng on it so I thought Ok no problem i just back it up on my second machine which has xp home sp3. During windows startup it finds out that it has errors on so it proceed to do error checking and fixing all well. So after backup. I put back the hdd back on the 1st machine. My question is why it didnt detect my ntfs partition ? Is it compatibylyty issue between ntfs with sp3 and ntfs with pre sp1?

Your best bet is to slipstream service pack 3 into the old Win XP disk with nLite. It is a reasonably easy process if you follow the instructions on the website

nLite - Deployment Tool for the bootable Unattended Windows installation - Download

nLite - Deployment Tool for the bootable Unattended Windows installation - Guides


Or you can go with this how to do a repair install from Microsoft...

Perform a Repair Installation