How to get rid of Linux! (or how to repair Windows boot record)
Having tried Linux you may decide it's not really for you.However installing Linux overwrites the Master Boot record used by Windows to boot up "normally", if I may use that phrase, and installs Grub or Lilo.
So to put the PC back to how it was, you need to Fix the Master Boot Record so that only Windows will boot.
After that, you can reformat and repartition the Linux partitions using GParted or Partition magic or even Windows' own partitioning tool.
On Windows XP, boot up the PC with the XP disk in the CDROM drive
(check your BIOS settings to do that - usually f12)
Select the option to Repair using the Recovery Console - option R
Select the XP option (usually 1 then hit enter)
When you get the C:>... prompt type fixmbrand hit enter
Ignore the nasty warnings and enter Y
Exit
Restart without the CD - should now go straight into windows.
At this point, rarely, rebooting can fail, to make sure it doesnt, just after using fixmbr (or go back into the recovery console via the XP cd if you have already rebooted), and at the c:> prompt type diskpart
Now use this to delete the previous linux partitions, leaving just windows partitions intact. After rebooting back to windows, to be sure of the empty space being clean for another distro, re-partition and format the empty space as a new partition, then delete it. A new distro now will not pick up on any data left behind from the previous distro (depends what filesystem was used but this is a possibility for confusing re-installations).
(Thanks to "Nige Laptop" for additional information)
Windows Vistais slightly more complex (Taken from Microsoft site)
Put the Windows Vista installation disc in the disc drive, and then start the computer.
Press a key when you are prompted.
Select a language, a time, a currency, a keyboard or an input method, and then click Next.
Click Repair your computer.
Click the operating system that you want to repair, and then click Next.
In the System Recovery Options dialog box, click Command Prompt.
Type BootRec.exe /fixmbrand press Enter. (There is a space before the forward slash)