0 byte Files

My system (WinXPSP2) generates 0 byte files for some reason. The files are
associated with other MS Office or PDF files and prohibit the associated
file and the 0 byte file from being moved, copied, or deleted. Frequently,
the MS Office or PDF files that are associated with these 0 byte files are
corrupted and unreadable; other times they are not. There is apparently no
virus per NIS 2008. I am looking for suggestions concerning the possible
cause(s) and solutions. I have been able to delete these 0 byte files with
Unlocker. These files interfere with backups and file maintenance.