The start of the New Year is always a good time to consider removing old data from your PC to boost performance before installing any new software you received for Christmas.

The three main advantages of removing old software are freeing up space, improving performance and erasing user history, says Hermann Apfelboeck of the Munich-based magazine PC-Welt.

As modern computers have such huge memory capacities, clearing up extra space is the lowest priority.

"Nevertheless, computer users should always check to see whether some programmes can be deleted such as multiple copies of the same programme," says Apfelboeck.

"New computers have almost no extraneous data," says Wolfram Meyer, who teaches computer classes at an adult education centre in Leipzig.

That is especially true for machines that are not connected to the Internet or only run a few basic programmes like word processing. But as soon as users start installing and removing programs, everything changes.

During installation, all programmes leave a record on the computer's registry, which is checked every time the computer is started.

Sometimes those registrations remain after a programme has been removed, meaning the registry can grow and slow down a computer's boot up time.

Additionally, some temporary files are placed in the folder C:WINDOWS/TEMP every time a programme is started up. Normally, those files are deleted when the programme is shut down.

"Conflicting programmes can lead to these files staying and multiplying," says Meyer. That means they have to be removed manually from time to time.

Defragmentation is another option for speeding up a computer, even if it is a relic from the days when hard drives were much slower.

Computers sometimes break up files and save them in different parts of the hard drive to maximize storage space. But breaking up the file means it can take a while to call its backup. These programmes make sure the files are saved in one piece, ideally speeding up the computer in the process.

Most junk data stems from the Internet as computers save histories, temporary Internet files and cookies to document their past internet contacts.

It is advisable to delete this information within the browser programme. Deleting this information not only clears up hard drive space, it protects data security. After all, other people using the computer do not need to know your Internet history.

Sometimes data has to be removed so thoroughly that others can never reconstruct or read it.

"Deleting isn't really deletion," warns the German Federal Office for Information Technology Security (BSI) in Bonn.

The files, folders, partitions and sometimes the hard drive have to be overwritten to delete them properly. Simply putting something in the computer's recycling bin and clearing that out is not enough and formatting the hard drive does not suffice either. To completely remove a file, experts recommend using special programmes.

Restoring an operating system can also require a lot of memory. Every time it is altered, Windows XP automatically creates a backup system so it can easily be called up in an emergency.

"That means one can quickly accumulate up to 100 backups," says Apfelboeck. If the system is running well, a user can set his preferences so only the most recent backup is stored.