Don't you just love computers?

I have three computers. One is obsolete in the extreme and only gets used as a word processor for writing my books and checking my emails. One is fairly up to date and runs on Windows XP and is my wife's primary computer. The last one is a shiny new netbook that my wife won in a contest and gave to me. It is the one running on XP that has given me horrors over the past several days. My wife called me into the office and asked why she was getting a message on screen that she could not save a file to the hard disk for lack of space. I had just defragmented it the prior week, and it had a ton of empty file space on it then. When I ran defrag on it this time, it showed only one percent of the disk was available. First thing I figured was, "Uh Oh! It's got a virus." I ran McAfee and an anti-spyware program, rechecked, same result: disk full. I started deleting files, photos, and programs. Even though I had apparently freed up beaucoup disk space, I got the same warning. It appeared that as soon as I freed the space, something wrote in it.
I am not a computer novice. I have built my own PCs, and serviced them when necessary, but this had me stumped. I had to contend for two days with my wife's grumbling while she worked on the old unit. Fortunately, my stepson is a network specialist, and we asked him to try to figure it out, which he did. He had some resources to which I had no access that enabled him to do so. It is running fine now. I am using it for this entry. I guess, like many people, I have a love/hate relationship with my computer. When they are working.