Try lowering your video setings , like texture size down to 256/128, on the initial AH startup screen.
Also goto Task Manager and watch the CPU usage.
Paraphrasing Skuzzy, it should move from 1% to 2% max fairly regularly, like a [slow] heartbeat. Going above 2% or higher usage indicates othr programs absconding with CPU cycles. This without AH running. With AH running, it should be very high, if not pegged at 100% with AH using the vst majority of them.
I think the above is XP related.
If this helps its more likely to be a resource issue I believe.