Upgraded Computer slows to a halt??

Hello all! I have been looking around your forum for quite awhile now as I have been wanting to upgrade some components of my computer. I got a Athlon XP 3200+ Barton with a new Shuttle mobo and 512mb of Kingston PC3200 in the dual channel config. I fired it up the first time and things were flying right along even with my Radeon 7500LE. That was a month ago. Over that time, I have noticed things started to slow down. Part of it was my defrag, and I think part was SP2 (don't quote me on that). So I fixed both and things picked back up... a little. In my optimism (and because there was a good sale) I bought a Radeon 9800Pro 128mb off the shelf yesterday. When I tried to install the software, I got the infamous blue screen and then my computer wouldn't boot. So, I rebuilt the boot sector and things were alright. In my small amount of wisdom I just downloaded the drivers from the net instead of using the same CD again... job done.Unfortunately, now this computer is almost to a dead stop. It has to think for a minute before doing anything. It took me about 3 minutes just now to get from the "Create a flight" screen to inside the cockpit. And once I was there, the HD kept accessing so much that I finally had to stop the program. When I have gotten it to work, I get about 6 FPS. Now mind you, it is at Simflyers' KMCO with the PMDG737, but I was getting about 12 FPS without the new video card. (That's still low in my opinion... I hear you guys get above 40... I would just love to hit 24! And yes, I have done all the tweaking that everyone suggests b/w stopping services and indexing, and adjusting virtual memory, etc.)So, thinking a little bit outside the box, I'm thinking that I might be looking at a degrading HD? It is a couple years old Maxtor 7200RPM 120GB. Can it just not keep up? Any thoughts would be greatly appreciated. I just don't want to go out and spend money on yet another upgrade that doesn't upgrade anything at all!Matt Perry