I am an experience puter user but not an experienced puter tech; I have done nothing more involved than installing a CD burner and the occasional minor software. I bought my last PC about a year ago with Win XP home edition already installed, and my system has become generally corrupted (probably from viruses and other junk picked up by SO when virus protection was temporarily absent), so I have decided go the down and dirty route and just start over from square one. Since I have no install disc, a friend gave me their XP Pro disc (and its product number). Last night I started by just inserting the disc and running the install. Part way through I was warned that another version of XP was already installed, and that the presence of both versions would probably cause grief and a general weakening of the nation’s moral fabric. I cancelled and decided to try the upgrade version of installation just to see if it would have any effect. It didn’t – programs that had disappeared were still gone, all my audio still plays about a half tone flat, etc. So I’m back to doing a complete re-install, which is fine, and what I had planned on all along. (I’ve already pulled off the files I care about saving and can re-load the few other programs I use.) But now I am unsure as to how to proceed – do I have to uninstall XP home first? Format the hard drive to wipe it completely? (But then it won’t boot up to the CD, right?) Do I need to worry about partitioning? (I grasp very little of its purpose or function.) Pitfalls, suggestions, guidance? Any help from those savvier than I would be appreciated.
If this product key has already been activated on their computer, this will be a problem. You will be unable to download any service packs or Windows updates from Microsoft, and it will nag you incessantly that this is an unauthorized copy of Windows XP.
I agree about the activation problem. It should be possible to borrow an XP Home disk and use the product code from the original installation, which is usually on a sticker on the back of the computer.
Anyway, you can wipe the hard drive - booting from CD does not require the hard drive. Just boot from the CD, choose the partition you want to install to, and you should be presented with an option to format the hard drive.
I just did this last week and found it kind of tricky.
I would suggest, the during the install, you reformat your hard drive and start over. Its kind of a pain but I think it cleans things up nicely.
Don’t forget to backup MY DOCUMENTS as well as any OUTLOOK addresses you want to save. Also, if you are a gamer, save you games from your saved game folder.
Wiping the drive will mean you will lose all the data on the drive. You do have a backup, don’t you?
Before you start, ensure you have a CD or memory stick with all the drivers, particularly for the network card.
Also, your PC may have a SATA drive, and by default, XP doesn’t know about these. Thee are two ways around this: in the BIOS set the SATA mode to Compatible, or install from an XP source slipstreamed with SP3.
In my experience you can use an XP Pro activation code twice before it asks you to contact Microsoft.
An XP Home licence doesn’t legally entitle you to use XP Pro, of course.
This forum isn’t the place to get info about hacking XP using somebody else’s Product ID number … that would get the thread shut down.
If your intent is to make a legal install you will need two things: your own Product ID number; it might be on a sticker on the back of the computer or stuck somewhere on the paperwork or CD that came with it … it is also possible it is inside the computer case or it may even have been stuck on the box the computer came in (which you threw away a long time ago.)
If you can’t find the sticker you can try to find your number using Magical Jelly Bean Keyfinder. Since you already tried installing another version it might not work.
You also need a CD containing the same version of XP you originally bought; you said you have XP Home and most likely it is an OEM version … so you need to find an OEM Windows XP Home CD.
With those two things ready, format to be sure all the gunk is gone and install.
What happened to the original disks?
Some computers have a double-super-secret hidden partition on the disk that stores the “originals”. There’s an option when you boot the computer to restore the disk to its original factory configuration. It will wipe the disk and re-install windows, all the drivers, etc. Not only does it save the cheap bastards who made your computer a few cents by not needing to give you a CD, it also makes sure that all of your drivers are installed properly, which is kinda nice. Unfortunately it also makes sure that any bloatware that came with your computer is properly re-installed as well.
If you have one of these types of computers, you won’t need a CD.
They went from XP to Vista, so it is no longer on their system. I don’t know if that changes the situation.
I didn’t intend to switch to Pro; I was trying to borrow a Home disk and couldn’t find anyone who had one. (I have my product code for Home taped to my tower.)
I do have backup of all the data I want, yes.
As for SATA and what follows… um, this is where I’m on the cloudy side. 
{Wish I was geekier}
Possibly. When you get the activation nag, do it over the phone with the number provided, and they will probably activate it that way.
That was my problem, I can’t find an OEM CE for Home.
I honestly didn’t set out to do anything illegal or unethical. I intended to use my 100% legal and legit XP Home license. (The difference between the two versions will be insignificant in my applications at any rate.) I will continue to look for a Home disc.
No original disks, already installed when I bought the tower - OEM, I assume.
Interesting about the other - how would I know if I have the super-secret mystery partition?
**THANKS TO ALL FOR THE INPUT **
When you boot, do you (however briefly) see a menu that has as one of its options something like “boot to recovery mode” or something like that? Sometimes it’s also an F-key option on the splash screen (something like “Press F11 to restore to original configuration”).
If all else fails, go to Control Panel > Admin Tools > Disk Management and see what partitions are listed for your hard drive, even if they don’t have letters.
Most manufacturers will supply a replacement disc at minimal cost (~$15) that will work with the OEM product key on your tower. Go to the manufacturer’s website and search for “replacement system recovery CD” or similar.
I’ll look and see (not on that computer right now).