Q: How do I change an image from BMP to JPEG format? We tried renaming the file but it doesn't work.

A: A BMP image is the native Windows format for images and is uncompressed. This means you have no loss of quality but the image file size tends to be large. JPEG images are highly compressed and work by using a special algorithm to encode the image, which results in comparatively small file sizes.

To save your BMP image as a JPEG, you will need to load it into a paint package that supports JPEG compression and save it, selecting this format in the Save dialog.

You will probably be asked to specify how much you want the image to be compressed. Be aware that there is a direct trade-off between compression and image quality.

Q: I want to sell my computer but the data on it is very sensitive and I have heard it is possible to recover deleted files. What should I do?

A: You are right to be cautious. When a file is "deleted" from the hard disk, the space is merely marked as available and the actual file is still there, so it only really gets deleted when a new file is saved in the space it used to occupy.

There are a number of commercial packages for deleting permanently, notably Burn It! by Syncronys and Nuts & Bolts by McAfee. In this instance, though, you may want to consider booting from a floppy disk and formatting the hard disk before handing over the computer.

Q: I have an infra-red mouse and keyboard and want to know if they give off harmful radiation?

A: Your fears are understandable but, in this instance, you can be reassured that your keyboard and mouse are perfectly safe to use. All computer equipment undergoes rigorous emission tests and has to meet high standards of safety.

Q: I have been offered a 21-inch monitor but it is very, very old - will it work with my brand new computer?

A: There is a possibility the monitor may have a composite output, in which case you could spend a significant amount of money on getting a converter lead. Ideally, the connector should be a standard D-type monitor connection.

You may also wish to consider the picture quality before buying. Older monitors can be prone to phosphor burn. This is caused by the electron beam (the thing that builds up the picture on the screen) gradually eating away at the phosphor on the inside of the screen. Why not ask if you can try it out with your computer first?