Disk Cleanup Utility

Well, it did compress them, from ~190MB to ~42MB space on the hard drive, so freeing up ~150MB. What sort of compression did you expect?  You would surely not expect the disk cleanup to delete them?  They are not unnecessary files, just ones that have not been used for some time, maybe some part of Windows or some app you don't use very often. When you need one, Windows decompresses it and then it would no longer be classed as old, so would not be included next time you used compress old files. The compression possible depends on the type of file, some can be compressed a great deal, others hardly at all. So depending on the files still regarded as old, the degree of compression can change.

 

Unless you are very short of hard drive space, I don't think it's a good idea to compress old files anyway. As you found ot the most you can generally free up is a few tens or hundred of MB, which is peanuts on modern drives of tens or hundreds GB . There is a small hit on performance as well, should some files need to be decompressed when they are used. If your hard drive really is nearly full, you would be better considering getting a second one.

Thanks so much for replying so quickly.  You were very concise and I now understand this.  Since I have alot of space left on my hard drive, I won't be that concerned.  Thanks again.