Windows 2000/XP/Vista

Google Desktop 
The most popular free tool for this is Google Desktop, available here for Windows 2000 or Windows XP. It’s also available as part of the Google Pack, which bundles a number of commonly-used Google applications together.

Google Desktop presents you with a very Google-like interface and will "crawl" through all of your local documents and e-mails on a regular basis to keep it’s database up-to-date. It’s a handy progam and easy to install and use.

X1 / Yahoo! Desktop Search
Google Desktop is pretty good, but my favorite desktop search tools are by a company called X1, which was recently purchased by Yahoo! These programs are much more agressive than Google Desktop about finding information in many different types of files scattered around your computer. The X1 search engine responds more quickly to searches and has a much better interface than Google Desktop for browsing through results.

I would recommend most people run out and download Yahoo! Desktop Search and the related file-type expansion pack and give it a whirl. This program is based on the X1 engine with a few added enhancements for Yahoo! users. Note that the X1 engine requires more horsepower than the Google Desktop search engine, so you may notice a slight slowdown if you have an older computer. In that case, simply uninstall the program and go back to Google Desktop.

If you’re feeling adventurous, try the X1 Enterprise Client, which contains a superset of the features found in Yahoo! Desktop Search but also has increased resource requirements.

Macintosh

Users of recent versions of Mac OS X have access to a great built-in technology called Spotlight that is about as good as the X1 search engine, though a touch slower. If you are using an older version of OS X, the Spotlight feature alone is worth the upgrade to the latest revision.

Linux

Linux users have the option of running Beagle, an excellent free search engine with many of the same features of X1 and Spotlight.

Conclusion

No matter what operating system you use, you’ve got the ability to search your computer as easily as you search the Internet. Never again will you lose an important document or piece of e-mail!

What search technologies work best for you? Please add your comments below.

                             -Brian