Your first goal is to establish whether your bottleneck is external (ie. from the Router to your ISP) or inside your wireless network.
Google broadbandspeedchecker, go to the site and click "Start Speed Test".
Depending on where you are, you should get a return of 6-8Mbits/sec. If it's a lot lower than that (say 1-3 Mbits/sec) then you're definitely not getting your full service.
Wireless networks are rated at 11-54 Mbits/sec, so in theory even with several devices attached and browsing the web, your network should easily be able to keep up with the much slower flow of traffic from the external servers.
Theory doesn't equal practice though. If the broadband checker says you a decent service, then the wireless network will need reconfiguring to ensure network packets are being delivered with minimum latency.
That usually means considering switching off the DCHP Server on the router, and setting static IP addresses on each connected device. Note down the router's own static IP, and use the same subnet, incrementing the last number by 1 or 10.
Try opening a CMD window (DOS prompt) on your laptop and type: Ping 192.168.1.1 (or whatever your router's IP address is).
You should get a reply along the lines of "Reply from 192.168.1.1 bytes=32 time=3ms TTL=64"
That represents a healthy connection. Any of those figures start climbing into 120ms or TTL=256, and you've got a poor wireless connection to the Router.
Other things to check:
Any laptop/device running something silly like uTorrent and downloading large files; running YouTube vids or other streaming.
Postion of Router - not next to a thick stone wall; installed as high as possible in the room.
As to the laptop and all the stuff it's running.. AVG is OK, but I tend to go with Microsoft Security Essentials. It's a *much* smaller footprint, works transparently without fuss, and is one less damn tray icon :smartass2:.
Black Viper's site is for the advanced user. If you're not sure what you're doing, I'd suggest you go through Control Panel/Uninstall Programs first, with a fine tooth comb.
G'luck
CS