If you really got bored with all the new looks and new features being offered with new windows vista and want to remove vista to free up some disk space.
But you may have installed vista in dual boot configuration with xp so i that case you have to adopt a whole new different procedure in order to uninstall vista.
Step By Step Procedure to Uninstall Vista in dual boot config:
Microsoft has released a very simple procedure to follow.
1. Boot your system in to Windows XP.
2. Ensure you have the Vista DVD image emulated or in the DVD drive.
3. Go to Start>>Run. Type e:\boot\bootsect.exe /nt52 ALL /force
4. You will notice the boot selection menu of vista now gone.
5. Format the partition/drive where you had Vista .
6. Remove two files Boot.BAK & Bootsect.BAK on your XP drives root folder (C:).
7. Restart to make sure that it works.
8. Merge the partitions together if you want.