you will get an HUGE improvement if you replace its internal hard drive with a solid state disk (SSD).
I installed a Trascend 64 Gigabyte SSD disk on mine and I can tell you that, with a fresh install of windows XP, it boots in less than 6 seconds.
Anyway you will see a good improvement (that does not require you to reinstall the whole operating system) you can upgrade its ram to 2 Gigabytes. (it is the maximum supported: you can't go beyond this limit with this pc)
Try it. you won't be disappointed at all.