Lest your local geeks-for-hire take you for a ride (or fleece someone you love), we’ve rounded up a representative sampling of typical repair-shop services to help you sort the rip-offs from the reasonable deals.

PC Tune-Ups

Just about every repair shop I’ve encountered offers some kind of “tune-up” service that promises to improve your PC’s performance by deleting temporary files, defragmenting your hard drive, removing unused applications, running Windows Update, and (in many cases) cleaning the Windows Registry. These services often cost $50 to $100, but generally they don’t do anything useful that you couldn’t do yourself with a free download and some utilities that come with your PC.

Before you shell out a hundred bucks, think about what this service entails: Windows comes with a utility called Disk Cleanup that will delete temporary files for you with a few measly mouse clicks. Disk Defragmenter–another built-in Windows tool–typically runs automatically on a weekly basis, but you can launch it yourself by going to Accessories, Utilities and clicking Defragment Disk. Windows Update also runs automatically by default, but you can click Start, type Windows Update in the search field, and run it yourself on command.

If you have a bunch of programs you don’t use, launch the ‘Programs and Features’ utility from the Control Panel and weed them out by clicking on them and selecting Uninstall from the menu above the main window. Or download Revo Uninstaller, a proven freebie that does a bang-up job of pulling out all the detritus that Windows’ uninstaller often leaves behind.

As for Registry cleaners, we recommend avoiding them entirely. Although the premise that removing unneeded Registry entries can speed up your PC is basically sound, there’s little evidence that it works in practice, and you can easily do more harm than good when you go mucking about in the Registry.

Not counting the time you’ll spend waiting for Disk Defragmenter and Windows Update to automatically do their thing, the total amount of time a relative novice should take to perform all these tune-up tasks is about 15 minutes. So save your money, and check out “Speed Up Everything,” our easy guide to giving a computer a performance boost without paying for dubious services.

Data Recovery

Hard drives can fail. Houses can burn down. Human error can result in lost data. When these things happen, you may find yourself weeping over the loss of all your digital photos, your music collection, essential business information, and more.

Professional data-recovery companies can typically get all of your lost data back for you (even from a fire-damaged hard drive), but you can expect to pay in the thousands for the service. It may sound like a rip-off, but these companies use advanced computer forensics systems that are wildly expensive in their own right and require deep technical expertise that you won’t find at the tech shop down the street.

The best way to avoid finding yourself at the mercy of data-recovery services is to back up your PC often,  If your hard drive fails, your computer burns up in a fire, or someone runs off with your laptop, you can get every bit of data back all by yourself. Compared with the cost of professional data recovery, $60 a year for online backup is a bargain.