Adding more RAM and video card ? HELP !

Adding more RAM and video card ?" Hello, kind of new here on forum and have read alot off the posts.My computer is a HP Pavilian a465c computer 3.00 gHz with 512 mb ram. I run MSX with acceptable fram rates with medium sliders (except autogen) in big cites and get 6-12 fps on ground and 20-30 in air. ok. Lots of freezes and puases while things load though. Jerky motions some times.My graphics is on board intell integrated graphics with only about 64 mb shared memory. Scenery is blurry ground not much texture on ground and can see cars but no roads, railways etc. Aircraft are sometimes blurry, I have my global scenery slider al the way right. Sometimes ac is sharp and not bluury. Sometimes for about 2 seconds I can see sharp great looking ground with roads and everything then it goes back to low texture and blurry.My memory is 184 pin DDR SDRAM, pc3200 . There seems to be a discrepency on HPs website for the product specification for this computer. The web says that the computr has 512 MB installed ( 2X 256 MB) and max allowed is 2 GB (4 X 256 GB) This doesn't make sence that would be 1 Gb. Board has 4 memory slots, two are being used. However, the Mother board spec sheet for this computer on HP web saids up to 4 GB PC32oo/2700/2100 DRR DIMM can be used in the four slots?.Would upgrading my memory to 1.5 or 2 gb help ? Can I mix 256 GB ram (DDR with a new 1 gb module ?My computer also has two free PCI and one AGP 8X/4X slot. Would an inexpensive video card add to my system performing better, and if so, what is a good inexpensive card.Any help would be greatly appreciated.