It might be that simple - it depends.
If you had XP installed first - XP partition will show as "system" when you are booted into 7.
If that is the case, boot the 7 dvd to command prompt, type:
bootsect /nt52 all
then press enter.
Should then be OK to delete 7 partition.
First, better boot into Windows 7 and post a screenie of Disk Management , to be sure.
http://www.sevenforums.com/tutorials...en-forums.html