DONT go & buy win7 for a laptop that old.  WORST>>ADVICE>>EVER
Win7 doesnt just grow on trees guys, you have to buy it :-)

Despite what some say, Vista with SP2 runs perfectly OK , on a descent machine. The issues with vista were pre-SP1 & it being
loaded on way underspeced machines. Vista SP2 is not that different than Win7 .

I'd agree that a re-install will do wonders, assuming the HD is OK .
Also , sometimes laptop CPUs will get stuck in Win power save mode (and run at less than 1/2 speed). Try disabling all power save when running on mains power & see if that helps.
Run MSConfig, start disabling startups & non-win services
Uninstall AVG completely . Install another AV (perhaps Avast) , AV only, not full internet security suite
Internet security suites that do everything except make coffee can sometimes be resource hogs

Registry cleaners are scams btw.

The specs on that laptop are pretty much last century: be realistic on expected speed. The more you install , the more things that will
be loading up on startup, slowing down the startup process.
Remember, it will have a relatively slow HD, & relatively slow CPU . Dont expect modern desktop performance.

If Win takes 3 minutes to load win, so be it.  As long as it runs OK once win has loaded, thats all that really matters
Ive seen plenty of old PC's that take 3+minutes to load Win & all the startups, just the way it is . Turn on, go make a coffee, come back.