High Cpu usage Causing game to lag

I have a problem with my laptop and this problem only happened recently,

When i play any game,Example, Warcraft, Gunz,roller coaster tycoon 3,and soo much more...but doesnt happen in runescape...
After 10 minutes of game play i start to lagg like crazy,
This never happened before and im not sure what to do.

my laptop has exceeded the minimum specs to play the games...
When i alt-tab,I see the game that i am playing having a memory usage of over 200,000k++
cpu usage also shoots up to 100% though it will go down to 70-90 when i alt tab...And if i leave my laptop with the game running, it starts to lagg and 10 minutes later its back to normall,and this process continues on and on...
I had no problems playing these games in the past,but now even when i reformat my laptop 4-5 times,it still wont work...


Here are my laptop's spec
Dell inspiron 600m
XP Profesional version 2002 SP1
Intel®Pentium®
Processor 1400MHZ
1.40GHZ
1.00GB ram


Chip type: ATI Mobility Radeon 9000 AGP(0X4c66)
DAC type:Internal DAC(400MHz)
Memory size: 32MB
Adapter String: MOBILITY RADEON 9000
Bios information: BK8.0.0VR008.019.008.002.007.001.001.001 F


Oh...and i have one more problem.
whenever i type "e" and "r"
the result would be having a "w" at the back and i must delete the "w" so my sentence would make sense.
Example if i dont backspace the "w"

:I havew tewnthousand dollarws in thew bank rwight now.
:you arwew onew laggewrw

If you take away the "w" behind some "e" and "r" my sentence would make sense...
I dont know why it only happens to these 2 keys...is it because of over heating???im not sure...i havent clean my fans at all since i bought my operating system...and when i lift up my laptop,the bottom of it feels hot...and not warm...but hot!...


I would appreciate any help from anyone