|If this is YOUR computer and you have already burned those files to DVD then you can delete them. You could also copy them to DVD media to save them for future use. |
What percentage of free space remains on the C partition of the drive?
If you can run defrag you probably have 15% free space.
I suspect the slowness issue is not caused by those files. You list 8GB of RAM. If you are running Windows 7 64 bit version then the computer shouldn't be using the swap file very much.
I would check for viruses and/or malware.
How many processes are running in Task Manager?