Computer Speed

Most people only realize this if they fill their drive.
On the older computers with 1, 2gb drives, they filled fast. An overfilled drive will cause a machine to barely crawl. Backup your data to a cdr, then delete it from the hdd, uninstall unecesary programs. Clean out all the temporary and junk files.
This utility will help with the latter.

CCleaner removes fixes registry issues, and cleans out all those temp files, and is very fast.
http://www.majorgeeks.com/download4191.html

While the computer's actual speed won't decrease, the larger the mass of files to sort through the longer it can take to locate and open them. Thus, it may seems as though your computer is slowing down a little. The best way to combat this is store archived data on CD/DVD/external drive and also to defragment your hard drive every so often.

Hope this helps,
John

Yes.

One reason is called fragmentation.
Which means your files are being split into small pieces to fit into the available space on the HD.

The available space maybe in small chunks all over the HD.

When you go back to get the file, windows will have to search all over the HD to retrieve all the small chunks...not good for perf...not good for the HD.