I use both PCs and Macs, for different purposes. On PC I installed Slackerware and Dumbian Linsucks, along with Windows .NET Codename Gundam for hacking purposes. It's a lot of fun and it works well, I tweak the OS every day. Macs are good when you want to type up a document, or do something creative and want it simple.
Simple Mac OS X:
To hide users, edit the AppleLogin XML files in /private/var/db and some other locations.
When root in enabled (manually), the Other user automatically appears and cannot be turned off without editing the XML files.
Windows XP, .NET Gundam:
To hide users, go to regedit and edit the \HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Special Users\Userlist keys, setting binary values for each user (usually 0 or 65535).
Administrator is automatically enabled, but:
XP Home: Only shows up and can be used in Safe Mode.
XP Pro: Doesn't show unless editied or Safe Mode. To use, press Control-Alt-Delete twice at UILOGON, only works if no other users are logged on.
.NET Gundam: Depends on your install of Winlogon, UILOGON, and MSGINA.
In terms of hardware, I get used computers.
Well, used
SGI workstations.