A slow computer can often indicate a failing hard drive. Your drive can fail at any time, so a back-up is vital if you care about your data. If the drive needs replacing, consider an upgrade to a “solid state” hard drive (SSD). The performance is night and day on most systems compared to a mechanical drive. These older style drives are still in heavy use, as they are still a bit cheaper, and are better at allowing for data recovery if there is a failure. Not withstanding, seriously consider the SSD as a replacement or upgrade (even if your current mechanical drive is healthy), make sure you have a backup of important data, and be amazed at the new life one can bring to your computer.
We currently have a coupon in the Passport To The Kootenays book for a free hard drive health test.