PCs that beep during startup are giving off a warning code, although the meaning varies from one PC brand to another. (James Best Jr. | New York Times/The Minnesota Star Tribune)

Q: I dropped my Dell Inspiron laptop on a hard tile floor. Fortunately, the PC still runs properly, and I ran some diagnostic tests that found nothing wrong. But now, every time the PC starts it gives a series of five beeps that are repeated five times. Do the beeps mean something is wrong? If not, how do I get rid of the beeps?

BRUCE BURTON, Bloomington

A: The beeps a PC makes at startup are a warning code, although the meaning varies from one PC brand to another. On a Dell Inspiron laptop, five beeps means that the CMOS battery on the main circuit board has failed (see tinyurl.com/35af53tn).

CMOS (complementary metal-oxide semiconductor) is a type of computer memory chip that stores some important data — the PC's BIOS (basic input/out system), how the PC's hardware is configured and the time of day and calendar date. The chip is powered, even when your PC is turned off, by a small round, flat battery that's similar to the batteries used in car key fobs. These batteries can last for up to a decade, so many PC owners never encounter the beep warning you're hearing. But by dropping your PC, you probably caused the CMOS battery to come loose from the PC's main circuit board, triggering the warning.

If that's the case, you should be able to fix the beeping computer problem by tightening the battery-to-circuit board connection (use a pencil to push on the metal clip that holds the battery in place), or, if necessary, by replacing the battery for around $2.

However, this fix involves opening your laptop and touching the main circuit board, which is very sensitive to static electricity (see directions and warnings for changing a CMOS battery at tinyurl.com/yc7jurdc). As a result, it might be better to let a repair shop do the work.

Q: My iPad previously sent documents to my printer using Apple's AirPrint feature, but now I get the message "No AirPrint Printers Found." What's wrong? Also, I recently discovered that I couldn't sign legal documents on my iPad. What's the solution?

PAT CLIFTON, Colorado Springs, Colo.

A: If you've recently updated the iPad's operating system, you may also need to update your printer's firmware (software stored on a chip) to maintain the printer's compatibility with AirPrint. Download a firmware update from the printer manufacturer's website. (See other possible fixes at tinyurl.com/2p953tmv.)

To sign legal documents on an iPad, get a free document signing app, such as DocuSign, PandaDoc or signNow from the Apple App Store (for details, see tinyurl.com/yckvtvmw).

Q: I have three old PCs with Windows XP. Can I donate them to anyone?

Edward Lassus, Jr., Metairie, La.

A: Most PCs with Windows XP (introduced in 2001) are too old to donate. The World Computer Exchange, a charity that transfers used computers to developing countries, requires that donated laptop PCs be no older than 2005 and use "dual-core" or newer processor chips. Desktops must be no older than 2008 and use Intel Core "i Series" chips. (See tinyurl.com/5n8r9wr3).

Steve Alexander, a longtime business and technology reporter at the Star Tribune, started this column in 2004 to answer readers' questions about their digital devices. Steve, who retired from the Star Tribune in 2014, is now retiring the column. This is the final one.