Windows Vista: Computer suddenly running very slow, no aero effects etc

Computer suddenly running very slow, no aero effects etc

Hi

My computer has just started being very slow. I installed vista months ago, and noticed a slight performance decrease, but nothing major; just the accepted from vista.

I recently installed C&C3, and at first it ran fine, but now it and other things are acting wierd.

Some of vistas effects (i.e. the scroll-through-windows thing) have reverted to the "basic" ones, which i dont particularly care about except it may mean my graphics card (7600 GT) is playing up.

Games run okay at some points, then will run unplayably slow for a few minutes intermittently, it does not appear to be on particularly "stressful" points. On C&C, it happens on loading a new screen (i.e. objective screen, then quitting & returning to the gameplay) or when a full-motion-video sequence occurs (when a movie-style video is shown).

Vista runs HORRIBLY - i have turned all the effects down so it looks like Windows 98, but it is still very slow at loading programs, folders and even typing.

Vista will not let me rate the system with the Experience thing - it says could not complete assessment, even though it previously worked fine.

I have:

1gb RAM
GeForce 7600 256mb
AMB Athlon 64 3000+
120gb HD
(vista 32 bit)


Thanks in advance for any replies, i really need some help here.

James