Slow Internet speed (not from ISP)?

[TreeRat]

So Charter came out and did a total diagnostic on EVERYTHING from the tap on the pole all the way to my computer. He even hooked his laptop up to the modem to prove the speeds. Now I have a very old PC with 2.06G of RAM. My computer won't show even HALF of what's coming into the modem. What's up and how can I fix it?
BTW....no virus, spyware, or any other bugs. Did a complete scan.
Oh yeah, the download speeds are jumping all over the place.

[Moi]

What are the other specs of your computer? Before buying another computer just format the one you have and use the Operative System it came with, it will be completely outdated and it's not safe to use it like that. If you update the OS and programs you are risking to bring your computer back to a crawl.

By the way even after a full scan the computer can still have virus.