I don't know if the person who started this thread is still interested, seeing he hasn't written here since 17-03-2012, but I'll here's my 2c. If a computer(laptop or desktop) is working harder and harder it might not be a hardware fault. The first thing you can do is reinstall a fresh copy of windows. Now...at a laptop...there are a few things that that tend to fail, and those are: the battery, the cooler, the hinges, the power jack, the HDD. If any of these has failed, this does not mean that the you have to throw away your laptop. You can buy a brand new battery, the cooler can be changed very easy(usually it is held in place by a few screws) and the HDD is very easy to replace. For the hinges and the power jack you can take your laptop to a technician and it will cost you a fraction then buying a new one.
To extend the life of these parts try to: - always plug in the power cord after the battery is empty and only when it is empty
- in an area without too much dust
- try to not open and close it tens of times a day(this repeated action damages the hinges)
- be careful not to trip on the power cord when the battery is charging
- when transporting the laptop try not to throw it on the back seat of the car or something like this or make abrupt movements because this could damage the HDD.
A laptop that has been taken care of, can work without any problems for around 5 years.