OK, so now I'm using a Win7 PC to post this, but my problem is with my older XP Pro SP3 PC. Long story that basically started with a problem with the software associated with a HP All-In-One. I tried to do a Repair from a corporate version of XP Pro SP3 and hit the R too quickly which started a Setup process, thank you MS. Now I've really screwed up by copying the System32\Config\System file from an older PC that was built from the same XP CD. Now I've downloaded and extracted Recuva to my empty,formatted 2TB extenal HDD. How can I get my life back? I can get to a DOS prompt using the installation CD and go into my C: drive and see all my files are still there. I want to be able to boot from the external HDD and run the Recuva tools. If I have to reformat the external HDD it's OK because I still have the unextracted Recuva file on this Win7 PC. Any suggestions?
Since you have access to your files, first step is always do a backup of anything you deem important. It's also ok to install the corporate XP, it will automatically create a dual boot and you can still attempt to repair the damaged one later. Unless you're cramped for HDD space the second XP OS will not mess your previous install settings, unless you clicked Upgrade.
I would say install the XP corp. edition anyways and backup your system the nice and easy way. As for booting from a slow USB external drive (ESATA recommended if you want true speed), as long as post screen shows your USB, XP should have no problem installing there instead, just know your drive letter when prompted to choose drives. Re-partition and re-format for a clean install is recommended on the drive in question.