The solution to deleting files on a Windows drive (XP or Vista) from Mac OS X is to use Paragon NTFS. Upon installing Paragon NTFS you’ll be able to copy/delete/modify files on drives formatted NTFS (all Windows computers since Windows 2000). This is especially handy for you VMWare Fusion (like me) or Parallels folks who need to continue using PC apps on their Mac for one reason or another.
Apple, which hasn’t licensed the use of NTFS technology from Microsoft, has only supported reading from Windows drives from OS X Tiger/Leopard/Snow Leopard.
There is also a free NTFS program for Mac called NTFS-3G which may do the trick for you, albeit with a little less polish (and perhaps stability) than the commercial solution above.