MP3 hi-fi
I am looking to replace an ageing hi-fi. With much of my music now on my laptop in the form of MP3 and WMA files, I was wondering if there is a decent home-based MP3, CD and DVD unit out there. I could then listen to music through a decent amp and quality speakers rather than my current soundcard/tinny PC speaker combo. Stewart Boyle

Jack Schofield replies: You could connect your laptop to your hi-fi system either directly from the soundcard line-out or via a device such as Xitel's HiFi-Link, or you could buy an MP3 player. It should be possible to connect this to a hi-fi amp using a cable that starts with a headphone jack and ends in two phono plugs.

Alternatively, many cheap DVD players such as the Yamada DVD 5520 and Pioneer DV-360S Silver (picked at random from Amazon.co.uk will now play back MP3 files from CD, as well as formats such as VCD, SVCD, CD-R, CD-RW, and Kodak Picture CD (JPeg). A growing number also support WMA (Windows Media Audio) files. A DVD-based system should sound better than a PC, though it is arguable whether most MP3 files could be described as hi-fi. MP3, WMA and Sony's Atrac compression systems are all "lossy".

This means audio information is thrown away to make the files smaller, and there is no way to get it back. Often this doesn't matter because the systems used to play these files probably wouldn't be able to use it. Unfortunately, the better your hi-fi, the more likely it is to expose the limi tations of the source, especially if you get the contrast of switching between MP3 files, CD or SACD discs or a decent turntable. Having said that, if your MP3 files have been recorded at a bitrate of 256kbps, I think you would be pushed to find many people who can tell the difference.

In the near future, there should be affordable DVD/HDD recorders with built-in hard drives, and some will connect to a PC via an Ethernet or Wi-Fi network. But I reckon silver discs will be around for a long time yet, for both storage and back-up.

CD saver
I use my computer to archive all my watercolour paintings, storing them on CD for safety. The original collection has nearly filled a CD, and it now resists playback, "freezing" the system. Alan Watling

JS: The CD format was designed to play audio in one long track, not for multi-session data recording or the sort of incremental or read/write "packet writing" approach that computers use with magnetic discs. Packet writing may be convenient and has its uses but, in the long run, it is unreliable, and therefore unsuitable for making back-ups. If you want a reasonably secure record, save your pictures on the hard drive or on a different removable medium until you have 700MB, then back them up by writing a whole CD at once.

Anti-spyware
I'm now spending a lot of time trying to keep on top of spyware of one kind or another, even with excellent programs such as Ad-aware and SpyBot, etc. Given that these programs alter the activities and sometimes the security settings of my PC, does this not constitute hacking? Why are the authorities not doing anything about it? Graham Wilson

JS: American lawmakers are aware of the problem and, in fact, last year, Republican congresswoman Mary Bono proposed a Safeguard Against Privacy Invasions Act, which would require companies to get users' permission before spyware is installed on their hard drive.

However, many people readily give this permission when installing free file-swapping software, media players, file downloaders and other programs. So-called "drive-by" installations should not usually be a problem if your software is patched up to date (including Java updates) and you are running, for example, SpyWareGuard from www.wilderssecurity.net/spywareguard.html and using SpyBot's inoculate feature. And, yes, Mary Bono was married to the late Sonny Bono of Sonny & Cher fame.

Backchat

· Simon Brooksbank wanted a way to find out if someone was trying to call him while he was on the net. Jacqui Morgenstein says: "Many (most?) ISPs don't seem to want to support modem-on-hold" so she uses a £29.95 Comtech Internet Alert IA510 instead. "You only need Call Waiting from your phone company and it works with V.90 modems as well as the new V.92 ones. When someone calls you, the red LED flashes and the unit beeps repeatedly." See www.comtechproducts.co.uk/tele/ia510.

· While discussing monitors last week, I should have said the Sony Trinitron uses an aperture grille. As George Haytack points out, "all colour CRTs have shadow masks".

· On the subject of losing email messages, Ron Bridle suggests writing in a word processor before copying them into email, so you always have the originals. "My way takes longer initially but, in the end, it is the best way," he says.