please advise what pc you are using with a full description of the following: motherboard, type of memory ie PC133, PC2700, graphics card, cpu rating (intel or AMD)
Photoshop is a processor hungry program and will struggle with an old one of a few years old. Together with the 64mb RAM you have, im sure your system is screaming at you to give it some extra juice.
I have a feeling that your machine is a few years old and may be worth looking a replacing the whole thing with a new one. There are some good deals at the moment with a brand spanking new pc costing as little as £500. You could easily spend that on a new motherboard, CPU, RAm, HD Graphics card.