I suppose the first thing I would say is if your machine is running ok and you intend to keep it a while, go onto a site like www.4allmemory.com or www.crucial.com, run their configurator, and see how much is would cost to upgrade to at least 2GB of RAM. 512 works for SP2, but it is really a minimum (thank you M$).
You could go into your Programs list and uninstall components you are not using of your HP Print package. Unfortunately, disabling the ink level indicator, in example, on their newer printers can also cause communication interruptions that stop the printer from working. The only things I can think of disabling that haven't caused problems for me on some machine are: The Yahoo Toolbar they load, SmartWebPrinting, and the HP Store. I have had mixed results with the HP Feedback.
This is not an AIO, but if you get those machines, the default scanning software, etc, do have a serious resource load. To get around the memory issue on those machines, there is usually a driver-only install on the HP website (designed for businesses) that will allow printing only and minimize the pain.