Egal,

One reason your system is slow (despite Internet performance) is that you are running memory eating processes you really don't need, like real player update, like quicktime task update, like Nerocheck, like.....(I saw others)

You have some housecleaning to do, not to mention some other Hijack items I saw.
Does every available option in AVG antivirus need to be running? I didn't count exactly but I thought I saw at least 4 different AVG files loaded.

Despite all this, please check your entire system, including hidden files and system files for "autoload.exe". See if that file is present. Please let me know if it is and where it is.

Also your system will run better if AVG is not scanning/filtering all files being used all the time, at least exclude some from run-time scanning and setup a nightly schedule scan instead.

Also if I had your system I would also add a 256MB or more stick.

Last but not least:

Is your video card an "on the motherboard" type?

Thanks.