Internet speed suddenly dropped

Hello,

In the last 2-3 weeks I have noticed that my internet speed is quite slow. Ive had the maintenence guy come by the other day and test the speed and it seems like there is a problem with my laptop since there are no connection issues. I am thinking there is some kind of malware since it has always worked fine up until 2 weeks ago. I tried to do a system restore but it didnt change anything. I posted this topic in the malware removal section but they couldn t find anything wrong with my computer

Code:

http://forums.majorgeeks.com/showthread.php?t=280045

They suggested I try my luck here so here I am.
My bandwidth speed is 15mb/s but it has dropped to 6-8mb/s every time I test the speed. And sometimes the speed test shows 20-25 mb/s which is impossible since the max I can have is 15mb/s

The maintenence guy connected his laptop to my router and got the full speed of 15 mb/s while I am only getting the half of it.

I use my laptop mostly for work but I also watch movies on it and browse the Internet etc

I hope you can help me figure out what happened.

Thanks,
Denis