However, not everyone is aware it exists, it excludes lots of file types, the results are generally poor, and it is very slow - unless users have indexed their hard drives. Since Microsoft's Indexing Service is obscured three levels deep in the search options, it is a safe bet not many people have.
Some users have turned to third-party programs such as X1 and dtSearch, and more recent free offerings from Copernic and Blinkx. Many more will have wished they could search their hard drives in the way they can search the web with Google.
Their dreams have come true. Users can now download a beta test version of Google Desktop Search, and European organisations can finally buy Google's Search Appliance, to provide Google-type search facilities across the whole enterprise.
The Search Appliance has been available in the US since 2002, but now companies elsewhere can stick the bright yellow box in their rack system for a starting price of £19,000. It is an attractive price for the hardware, software and support, but it will only search 150,000 documents. If you want more, you have to pay more, and this will eventually lead to a hardware upgrade.
Google Desktop Search is, by contrast, free. Although the results are somewhat limited, it is easy to use and terrifically useful. It provides almost instant access to many files and, like Google on the web, it has a caching system so you can see an excerpt in the search result.
Many of the limitations are due to the fact that this is beta software. For example, it only works with the local C: drive on a PC running Windows XP or a patched version of Windows 2000. It mainly searches texts and Microsoft Office files, and it only tracks websites visited in Internet Explorer. However, we can expect Google to take in minority systems in the future.
It may even be that Google has launched Google Desktop Search a little early, as a pre-emptive strike. The HotBot search engine has long had a desktop search tool, and rival programs are coming soon from AOL, Microsoft and Yahoo. Microsoft says its desktop search will be out this year, but it will not be the next to launch.
Google's offering has had a mixed reception, mainly because of privacy concerns. Install Google Desktop Search and anyone who sits at your PC for a few minutes will be able to find pretty much anything you have on your hard drive - probably including passwords.
Maybe people using your PC could have done that anyway, but the ease with which Google can find things may make them more likely to try. Either way, this is one of the things companies will have to consider when they decide whether to allow Google Desktop Search into the enterprise, or block it.
Jack Schofield is computer editor of the Guardian