Normally I would say get rid of the X1900 if you plan to continue to use it.
You have been cleaning it every 3-4 months, as those cards are terrible on dust and heat.
Also get down to one good set of RAM or just pick up a 4GB kit 2x2 $25 from Amazon.
While at it, can't hurt and definitely a big plus to go with 250GB $139 Samsung EVO SSD.
Got a good older clone? should. Every freeze and crash is likely contributing to more corruption of ifles and directory making it worse. So good idea to start with new RAM, newly formatted drive, clean install of system.