There was a time when I could edit well enough, and I'm not sure what happened (it's not a virus), but now I cannot even play through a rendered timeline in premiere without it lagging like fuck. I have basically employed the 'guess and check' system where I guess at what cuts I should make, export, and watch the export to see if it looks okay. This is pretty shitty.
What's worse is that my computer should be able to handle playing UNRENDERED timelines, so it's doubly ridiculous.
This problem is the worst when editing lossy footage (obviously), but it also occurs when editing lossless footage. So whatever is going on, it's affecting everything (in Premiere).
I'm using Adobe Premiere CS5 (5.03).
These are my specs:

I'd like to know if something is wrong with my settings in premiere, or if I am misunderstood on my hardware specs. Or anything really.