Notebook computer might be stolen or lost. In this case the most vulnerable is information that looks like deleted, but is actually available for covering. Another problem is internet activity. Any Internet browser leaves a lot of traces, including the links to visited sites, used loggings and sometime password. This aspect may lead to identity theft problem, when someone could take a lot of information about you from your PC, from browser cookies.

If trying to solve this problem, we should understand that first, we need to know what is the source of potential danger and in what way can we manage these risks. I'm sure you are concerned about using credit cards online, but simple rules will help to use your credit cards only on trusted web-sites, and your data will not be stolen. So you keep using your credit card getting benefits of purchasing online.

The first simple recommendation about staying secure is: "keep your sensitive files in secure place". It's not hard now as there exists freeware and open source encryption systems, such as TrueCript. Another approach is to use encryption system of end-user programs, such as encryption suggested in zip file format or word files. Cryptology algorithms there are very hard to crack (actually, someone will be able to find the password only using brute-force analysis). If you send sensitive file to your colleague, use a password protection for this file or put this file into protected archive.

Communicating with others is a serious secure aspect. If you will use simple encryption systems, then before communicating you will need to exchange the password, this might be not very convenient, that's why it's a better idea to use one-key cryptography.

The second task is to make sure that your data is easy to undelete. Use file shredder to secure delete (wipe file), better idea is using background mode file shredder, which doesn't need your action to secure every deletion. Schedule regular wipe free space operation, this is not really 100% security, but it will keep about 98% of previously deleted data secure. How to choose file shredder to use? Download some free or free-to-try undelete software and check if files wiped with file shredder are recoverable. There might be some other security aspects (such as temporary files), but for most users it's quite enough.

The frequent question is - how many passes do I need? Actually, the answer is 1-pass overwriting during wiping is enough. The idea of overwriting data several times was suggested by Peter Gutmann in 1996. Where hard disks were much slower, small in size and worse in quality. For nowadays disks this idea is not really applicable and one-pass overwriting is enough.

Staying secure at the web. It is not a hard task, consider installing latest version of web browser, FireFox is great new software. Consider using firewall that is built into the system or is distributed as a stand-alone tool. Don't pass your data to the web-sites that you don't trust. Web-sites that accept credit cards must support secure protocols for purchasing pages. As for identity theft problem, the good idea is to read more about possible ways for intrude to steal your personal data, there is no much software that might help with this.

Finally, my recommendation is: make sure you keep files in secure place and make sure it's not possible to find your files somewhere else, for instance, undelete previously deleted files. It's simple, but it's a good way to stay secure.