My Laptop is very slow on the web.... What can I do... ?

I need your help again... I have a problem with one of my lap top's. Its getting worse each day. I have a wireless connection, and the problem with slow / bad connection is ONLY with one of my lap's.. I have installed C-Cleaner, Spyboot Search & destroy, Spyware blaster and bought the very expensive NORTON 360.. The free space on the disc's C & D are over 20 %...... Do I really have to format the disc's again ? It seems to always be the advice I get..., but I rather don't, if I don't have to, off course.... Is it any more programs I can use to fix the connection ? Or other good avdvices ? Backman