Well - I don't know what temps under XP would be... Vista and Windows 7 use the Cool'n Quiet. However, there is a tool for XP to use it so the thing isn't just pegged at 100% clock speed all the time. Make sure your heatsink, fan, and vents are squeeky clean. It would probably be best to pull it apart to do this.
Do like what was mentioned - replace the thermal pad or tape with thermal compound. It need not be some stuff that costs $15; but, most alternatives to the original will do better than the stock junk. Staples sells Arctic silver if you want to get something locally.
Watch out if you're northbridge on the motherboard shares the CPU heatsink setup - if it uses a thick thermal pad you will NEED the pad or else you will have a gap! However, you can lightly coat the pad for slightly better thermal conductivity.
Last but not least... call it a Notebook, not a Laptop - cause if you use it on your lap, or on your bed... you will kill it from blocking the vents.
The CPU max temp is supposedly 95c or 100c... shoot for less than 70c.