1. Your Wi-Fi network is now dog-slow. If it's not a network outage, you likely have interference. Try relocating your router to shield it from disruptions such as microwave use or calls from a cordless phone. Or you may be on a crowded channel. Change the channel via your router's configuration page; look for a 'Channel' section and try 1, 6, or 11. See "How to Improve Your Wi-Fi Network's Performance" for more ideas.

2. Your display looks terrible. Check display settings by right-clicking the desktop; choose Properties in XP or Personalize in Vista, then Settings. If you can't increase resolution and color quality, click Advanced, Adapter. If Standard VGA Adapter or another generic adapter is listed, download a driver specific to your PC (see How to Reinstall Windows XP for details on doing this). If your adapter is there, try a prior driver version. In XP, click Properties, Driver, Roll Back Driver; in Vista, open the Personalization Control Panel, choose Display Settings, Advanced Settings, Properties, and click Driver, Roll Back Driver.

3. Your printer is spewing out garbage. A cancelled print job may not have cleared properly from the printer's memory. Turn the printer off for a minute, then back on. While you're waiting, go to Start, Printers and Faxes in XP, or Start, Printers in Vista, to delete anything in the print queue. If the problem continues, download and reinstall the driver.

4. Your default printer is no longer the default. Some apps, like Microsoft's OneNote, install faux-printer-like devices as output options, and some will also unhelpfully make them the default for all print jobs. Select Start, Run, type control printers, and press <Enter>. Right-click the printer you prefer, and click Set as Default Printer.

5. You see daily, consistent error messages citing memory problems. To check if bad RAM is actually the trouble, download the free MemTest86 and stick it on a boot disk; then run the full battery of tests.

6. Your PC starts up too slowly. Click Start, Run and type msconfig. Then click the Startup tab to see all of the apps that load at startup. Uncheck anything you don't want to start at boot-up--but uncheck programs one at a time, as you need many of these apps to run your PC. (For more on pruning safely, see How to Make Windows Start Up Faster.)

7. Videos play sans audio or image. Your codecs are probably out of date. Get multiple updates via a free pack such as the ACE Mega CodecS Pack or the K-Lite Codec Pack.

8. You broke a key off your keyboard. If part of the key mechanism is broken, consider scavenging an unused key (<Insert>, perhaps) and use its mechanism with your broken key (Apple's tutorial at PowerBook G4: Keycap Replacement will walk you through the procedure--it should work for almost any keyboard). Replacement keyboards for laptops can usually be found on eBay for $40 or less; many step-by-step guides show how to do the job, such as the one for a Toshiba laptop keyboard at Laptoka.com's page, How to remove and replace laptop keyboard yourself.

9. You bent a pin on one of your PC's ports or cables. Using pliers will probably make things worse, but the tip of a large-diameter mechanical pencil will fit most pins. Just slip it over the bent pin to straighten it out.

10. Folders show only large icons. Change the default in Windows Explorer by setting the right view on any folder, and then click Tools, Folder Options. Click the View tab, then Apply to All Folders (Apply to Folders in Vista).

Upgrade with care: Support techs report that the most troublesome laptop components are the hard drive, screen, and keyboard. While you probably won't want to replace an expensive laptop screen, anyone with the right tools and even a slight mechanical inclination can replace the hard drive, keyboard, and other components, with some patient tinkering.

Opening your laptop case may void the warranty, so if your system is still under warranty, let the manufacturer deal with repairs. Notebooks are delicate, so never force anything. Vince Dougherty, who has repaired countless laptops for Wine Country Computers in Healdsburg, California, says the most common mistake is using the wrong-size screwdriver. One slip and your motherboard is ruined.

Before doing anything else, remove the notebook's battery and disconnect its power cord. Remember to ground yourself before you open the case, either with a grounding strap (the safest way), or by touching a piece of grounded metal (a lamp or water pipe will do), while touching a metal part on the case's exterior.

Replace your hard drive: Adding a new hard drive to a laptop is usually easier than doing the same thing on a desktop PC: You just remove a few screws from the bottom of the case, slide or lift the hard drive assembly out of the system, and swap a new drive into the assembly (always handle drives by the edges).

Most notebook PCs use a standard 2.5-inch hard drive, but ultralights and other diminutive systems may use a smaller 1.8-inch drive. Drives also come in different heights; the most common are 12.5 millimeters and 9.5 millimeters. Check your laptop's documentation, or visit the vendor's Web site to determine the drive size compatible with your machine.

A 2.5-inch, 100GB drive costs less than $200. Third-party vendors such as Drive Solutions and NewEgg.com often charge less than laptop manufacturers. Check with your notebook vendor to find out whether you need a SATA or parallel ATA model. Buy only from vendors that offer a money-back guarantee--any reliable seller will provide one lasting at least 30 days.

Boost your RAM: Most laptops come with only one or two memory sockets, which may leave no open slots for upgrades. Adding memory may require that you discard at least one existing memory module. The RAM on most laptops resides behind a removable panel. The modules slip into a slot and are secured at the ends by clips or retainers. Crucial offers an excellent tutorial on installing laptop RAM.

Crucial and Kingston will tell you the type of RAM your laptop needs. The high-quality modules they sell are well worth the small, additional expense over no-name RAM.

Change your keyboard: Installing a new keyboard usually requires disassembling the laptop's case, but in other respects it is straightforward: First snap the old keyboard out, and then snap the replacement keyboard in. You can expect to pay $50 to $100 for a new notebook keyboard. Appropriate replacement keyboards may be available only from the notebook's vendor.