if you're running XP and have anti virus and firewall running, I would strongly recommend upgrading to at least 512, or more, depending on budget and motherboard slot availability.
Virtual memory is very slow compared to real memory, XP and all the other things that pretty much have to be there for safety is probably using about 320 before you load any application, so even loading just IE will mean it's into virtual memory, which will slow the machine down, and if you happen to be using Norton, it will be a serious slow down!
Best of luck with sorting it,