[Stuart]

Sorry, didn't mean to be patronising. If you have installed all the software I have mentioned above, and made sure it updated itself, and run scans, the chances are you don't have any spyware.

How do the individual programs affect performance?

Adaware doesn't (unless you activate the "Tea Timer" System Settings protection setting), it requires that you scan the system from time to time.

Spybot, again, doesn't use any resources (it actually adjusts settings within the browsers to stop them installing spyware rather than preventing the installation itself. As with Adaware though, I would advise you scan your system regularly though.

Spywareguard and Windows Defender both do use some resources, but TBH, they will not impact your connection, and don't seem to use many resources (put it this way, I have them all installed on the Laptop I am currently using. The connection I have at work is far faster than 10 Meg, and network speeds aren't affected).

---------- Post added at 19:15 ---------- Previous post was at 19:05 ----------

I am not saying it is definately spyware, but this is one possibility.

The way that spyware slows down your connection is by literally flooding it with connection attempts. It's possible that this is causing the CPU in your router to overload, and effectively hang.

It can also be an incompatibility with the router. I know that networking hardware follows standard protocols (so you can mix and match hardware from different companies), but we have found at work that our machines with onboard intel NICS occassionally cause our 3com switches to do exactly what you have just described (slow down the connection). We ended up replacing the Intel onboard NICS with 3Com cards and all is well.