I disabled all avg services except the updater, which I set to manual so it updates. Removed all startup entries in msconfig. Inside AVG itself I disabled realtime & email, but left the shell extension turned on.
I don't mind updating avg and scanning manually, and I don't want real time protection all the time since I'm pretty safe online and don't want it on when I game, however if I do download anything, I don't want to have to do a whole scan since I regularly scan with several scanners that come up clean, I just want to right click and scan the file with avg, hence I leave the shell extension on as its definitely worth the tiny tradeoff in ram usage.
Lastly I use autoruns AutoRuns for Windows v8.71
and untick other useless startup items and all avg entries except for the shell extension and avg 7.5 still works perfect and it further lowered my overall ram usage and xp feels extremely responsive even on my old machines.