Windows XP has many hidden applications which can be accessed by typing their executable name in run!
Character Map = charmap.exe (to find unusual characters)
Disk Cleanup = cleanmgr.exe
Clipboard Viewer = clipbrd.exe
Dr Watson = drwtsn32.exe (Troubleshooting tool)
DirectX diagnosis = dxdiag.exe (Diagnose & test DirectX, video & sound cards)
Private character editor = eudcedit.exe (create or modify characters)
IExpress Wizard = iexpress.exe (Creating self-extracting / self-installing package)
Microsoft Synchronization Manager = mobsync.exe (appears to allow synchronization of files on the network for when working offline. Apparently undocumented).
Windows Media Player 5.1 = mplay32.exe (Retro version of Media Player, very basic).
ODBC Data Source Administrator = odbcad32.exe (something to do with databases)
Object Packager = packager.exe (to do with packaging objects for insertion in files, appears to have comprehensive help files).
System Monitor = perfmon.exe (know your system’s performance)
Program Manager = progman.exe (Legacy Windows 3.x desktop shell).
Remote Access phone book = rasphone.exe (documentation is virtually non-existant).
Registry Editor = regedt32.exe [also regedit.exe] (for hacking the Windows Registry).
Network shared folder wizard = shrpubw.exe (creates shared folders on network).
File siganture verification tool = sigverif.exe
Volume Control = sndvol32.exe
System Configuration Editor = sysedit.exe
Syskey = syskey.exe (Secures XP Account database)
Microsoft Telnet Client = telnet.exe
Driver Verifier Manager = verifier.exe (Driver monitoring).
Windows for Workgroups Chat = winchat.exe (Application to Chat on a LAN network).
System configuration = msconfig.exe (can use to control starup programs)