Treacherous Computing WarningIf you use Apple or Microsoft products, your computer has already been hacked by design. While previous versions of Microsoft Windows have had some advantages to offset the problems, the new licensing and Digital Restrictions Management (called Digital "Rights" Management by some) features in Windows XP and Vista make it truly a force for evil. Microsoft calls their new DRM "Trusted Computing", but it is actually Treacherous Computing. Microsoft applications with DRM (currently only Windows Media Player in XP), among other things, delete banned documents on demand. Microsoft Word is next to get the DRM treatment, and I hope you can understand the implications enough to shudder (remote global censorship). One reason why Vista is so much slower than XP is the additional work done by the OS to enforce new and stricter DRM.
The whole point of DRM is to prevent you viewing or playing Music, Video, or documents that you are not allowed to (by encrypting the data), even when you have "bought" the media. When you "buy" DRMed media, you haven't really bought it. You are only renting the privilege of viewing it - which the owner can take away at any time. For example, when suckers bought DRMed NFL video, they were able to watch it for a few months. Then NFL decided to change their DRM keys. No more views (unless you "buy" it again). Then there is the guy who made the mistake of tying class notes to a DRMed copy of '1984'.
If you have Windows applications that you can't replace, stay with earlier versions of Windows if you possibly can (of course, this will mean you can't read documents produced by later versions). Better, don't use Windows. A very popular Linux distrubution is Ubuntu. I myself use Fedora Linux. Both run on the same hardware as Windows (except for some WinModems and other hardware with secret interfaces - another Microsoft Evil).
One of my coworkers uses an Apple PowerMac. MacOS uses more expensive (but superior) hardware. It also has DRM, and all apple products keep a permanent forensic record of all files downloaded by any application. Encryption features offered by Apple include a back door allowing Apple to decrypt (in response to a court order, for instance).