|Deleting your cookies will not harm your computer. What you could do is download CCleaner (google it) its a free cleaner which will delete all your temporary files and cookies. |
You say that you scanned your machine with various virus programs, can you tell us what programs you used? my recommendations are below:
AVG Anti Visrus
Spybot search and destroy
the above are all free and very good, with a good scanning regime you can be sure your machine stays clean from virus's.