You said your IBM Thinkpad is about 4 years old
but the last I remember as IBM branded were the T-40 series. They became Lenovo after that. In any event, if yours was a factory installation, you should have a recovery partition and a Lenovo tool to do either a full or a repair installation. You didn't provide the model number so we really don't know how old yours is. It's a matter of pressing a key or two doing startup which will bring you to an options menu. If you cannot even get into safe mode, you can possibly recover your data before blowing things away. You can either boot from some Linux live CD (which you'd have to make from another PC) or you could put the hard drive in a USB external case and access it from another computer.