I would suggest that you can probably gain some speed by using cablenut.
Get the program at
www.cablenut.comThen use the Cable & Dsl 1500 custom file found in
Van Buren's Cablenut Settings v8
It is also possible that you may need to optimize your wireless network. Read about factors affecting wireless network performance
HERE.
Furthermore, you can visit the website of the vendor of your wireless adapter to download the most recent drivers. Try
HERE.
As it is always a good idea to use multiple virus scans to ensure that you are properly protecting your PC, try this online scan:
www.ewido.net/en/onlinescan