Sounds like overheating, It's rally not that difficult to get at the fan and clear out the fluff that gathers there over time. If it's a few years old, try reinstalling windows. If you're running XP, and the laptop meets Win8's minimum, get a Win8 Pro upgrade before the end of January or better still, take the plunge and install Linux instead. I can't recommend Ubuntu (any version) because of the privacy concerns over their sharing search info, including local hard disk searches, with Amazon. Mint is a very good starting point for Linux Main Page - Linux Mint
as is PCLINUXOS So cool ice cubes are jealous » PCLinuxOS
. If your laptop is Still running XP, then one of the lighweight linux desktops (XFCE is available with MINT or both XFCE and LXDE are available with PCLinuxOS, but I'd recommend LXDE in that case, as PCLOs's XFCE is currently a very old version, awaiting a new one soon). That's just a starting point.
PM me if you want any advice about partitioning HDDs and/or dual booting.