I have a computer with 2 installations of Windows XP. One is fully installed and in use, but the other one is only partially installed.
How can I remove the partial installation of Windows XP, while keeping my full install intact?
You need to find out which disk drive or disk partition has the fully installed instance of Windows XP. Then find out which disk drive or disk partition has the partially installed instance of Windows XP.
Then re-format the disk drive or the disk partition with the partially installed Windows XP. This operation will erase all the files on that partition, so make sure you save the files you need from it.
You may use Windows Explorer and Computer Management in Windows XP for these tasks. For the re-format you will have to use Disk Management tool. You can access it from the Computer Management.
How To Use Computer Management in Windows XP:
Before you do anything, make a backup of the valid install of windows XP, in case something accidentally screws up. Better yet, use a backup software that will fix your bootloader as well - I tend to use macrium reflect free. Make a recovery cd for your backup software - preferably the alternate one which works better on odd hardware. MAKE SURE THIS DISK BOOTS and do a dry run to make sure you're familiar with the restore process. Assume everything is going to go bad and all your data will be lost if you mess this up, cause it could and recovering from this sort of thing is unnecessarily hard and a pain.
Now that i've instilled a proper amount of fear, format the old disk from the disk management snapin. Reboot and Pray.
If you formatted the right drive (windows won't let you format the drive you're on), and the bootloader wasn't on that drive, it'll boot right up. If it was on the new install, it'll complain about the lack of bootloader. Pop in the macrium reflect bootcd and see if it lets you install just the bootloader, else restore the whole imaged valid install to the disk.