Here's an update. My HDD is 20GB and had only 800MB of free space. I bought a 500 GB external drive, partitioned it and backed up my entire system to it using Acronis. Then, after checking to be sure the temp file was there in the backup, I deleted everything in the temp file. Result: 4.5GB of free space on the C Drive, and everything seems to work properly. I guess you could say the problem is solved, at least for now. Thanks for all the input.