Maybe it's because of copy guarded programs, maybe it's because you loaded all kinds of system cleaners. Could be either or both. Do not install multiple security systems or multiple system cleaners in a computer, they conflict with each other.
Pretty much every process in the computer is running whether it's closed or not, every time you start the computer. Check the process manager, you have about 52 processes or more running full time in windows XP. Something that was installed affected the systems ability to defrag, it could be a microsoft update or anything else. Perhaps if the processes were stopped one by one the offending process could be pinpointed.
But troubleshooting requires that we do not assume anything, but rather, test everything.
Microsoft process explorer (a download from microsoft) allows you to shut down, halt processes to do your trouble shooting.