Want to go back to xp 3pk professional

Why on earth would you want to do that? Windows XP is more than a decade old. Learn to use Windows 7

I agree with Pinhedd,

But if you still want to go ahead, you'll have to do a full reinstall then,

Backup your data, format, reinstall...

if it's a new computer that you never used windows xp on before make sure you have all the required drivers to do so, some new hardware might not have xp drivers.

By the way, all version of Window XP are 32 bit apart from XP Pro, which has a 64 bit version of it. So you may have problem with the OS recognising all of your RAM, if you have more than 4GB of RAM and your copy of Window XP is not XP Pro 64 bit. Window XP don't have DX10/11 (if you are a gamer), don't support TRIM (if you use SSD). Apart from the driver issues you may have, I advise you to stick with Window 7 if you do not have a XP Pro 64 bit or if you are a PC gamer or a SSD user.

Windows XP Pro x64 is actually based off the Windows Server 2003 kernel, NT 5.2 rather than XP which is NT 5.1. Since it was an OEM only operating system there's barely any modern driver support for it. It was a sweet gaming OS for a couple of years though

Actually drivers for XP-64 are still being made, AMD and nVidia support it even on their top cards as does Intel.

Ya i was running XP pro 64bit before win7 came out I didn't have any driver issues. I actually used Gparted to make a new partition for win 7 just in case i ran into any problems with anything. I laugh about that now since from day 1 with win 7 its been smooth as silk. I'd never go back to XP. As good as XP was Win 7 blows it away now.