removing dual boot

I am using win xp as the main OS and i have vista as a secondary one, (dual boot and on a second partition). if i choose to remove vista and keep xp, am i able to go into xp and dekete all of the files on the vista partition, or do i have to format the partition to remove it. the dual boot menu on the other hand ill deal with myself. (if i cant remember how i will submit another question) thanks

sam