Actually, MAG, all we've suggested so far is how you can find the information that you need to give us, so that we can guess about what the problem is and try to help you get started with finding the problem.

The System Information utility should tell you what operating system you're using, and how much RAM you have.

The hard drive "Properties" will tell how large your hard drive is and how much free space it has.

Disk Cleanup is a generally good thing to do occasionally, and will help get rid of some temporary clutter. (If you've been trying to watch movies and any temp files from them haven't been cleaned up, that could be your problem since video files tend to be VERY LARGE.)

The Disk Defragment will make things on the hard drive more "orderly," which generally helps the drive perform better. It also will give you a number - "percent fragmented" - that might be helpful for us to know, even if you don't actually run the defrag immediately. You can have it "Analyse Drive" to get that reading, which is quite a bit quicker than actually defragmenting.

If you haven't done so recently, running defrag would be a good idea; but even a 160GB drive may take 6 or 7 hours - or more if it's really full or badly fragmented - to do a full run.

John