|The ideal and guaranteed way to get your laptop running like new is to back up all your data to another drive then run factory recovery to re-install Windows afresh.|
I did that for my sister's work-colleague last week (her laptop was really slow) and she says it's like new again since my 2 days working on it to sort it out.
Short of that,
1) Check that you've got as much RAM as your system & the OS can support, since AVG is known to be a very heavy user of RAM (the laptop I fixed had AVG on it, one of the main reasons it was struggling, so I ditched it in favour of Comodo). I know it's only Windows XP but even that benefits from as much RAM as you can give it (it supports up to 3.5GB for the 32-bit version, in practical terms that means 4GB installed).
2) Run the Disk Defragmenter on the main system partition as fragmented data can affect the speed of data transfer and slow down the opening of applications:
Start > All Programs > Accessories > System Tools > Disk Defragmenter
3) Windows Startup Time: keep your start-up modules under control (the items that start automatically when Windows starts). Many of them just aren't necessary yet every one of them takes a bite of RAM for itself, leaving less for Windows & apps.
Ccleaner is the best utility for disabling unnecessary start-up components:
4) Don't let free space get too low on the main system partition as when it does Windows has insufficient space to operate efficiently when it's swapping out data from RAM to hard drive & vice versa.
If necessary, uninstall large apps you hardly use. Also consider moving your docs and pictures etc. to an external hard drive (you'll actually need two of them so you've got a backup).
message edited by phil22