Dell :: Inspiron 9200 Hardware

I have a Inspiron 9200 that I purchased about 4.5 yrs ago and will be replacing it w/ a Studio 1555.

One of the main reasons is b/c there is something seriously wrong w/ the laptop where it goes extremely slow all of a sudden but especially with watching videos. I can barely watch videos on itunes since every starts going really slow. Playing videos using VLC player helps a lot but other task such as simply minimize a window takes forever. Another big problem is the fans. They are extremely loud when they turn on and the bottom of my laptop gets real hot. Im thinking this is a serious hardware problem since I've tried doing a fresh install of windows XP and i still have the same problems. My friend who knows a lot about computers opened my laptop about year and half ago and found a whole bunch of dusty balls in the fans. He took them out and my laptop fans were not loud anymore and my laptop was a little bit snappier but its gone back to its old ways. What I want to know is what are some possible explanations for the slow down.

Here are the specs for the Inspiron 9200

Pentium M 725 (1.60GHz)
17" UltraSharp Wide Screen XGA+ Display
512MB DDR 333MHz 2 DIMMS
128MB ATI Mobility Radeon 9700
40GB Ultra ATA Hard Drive
Windows XP SP2
8X DVD+/-RW Drive
Intel PRO/Wireless 2200 Internal Wireless (802.11 b/g 54Mbps)
53 WHr 6-Cell Lithium Ion Primary Battery