How can you tell? It has windows media center, its a Dell and was purchased in November 2005. It did not come with a remote control

Right click my computer and left click properties. It will say media center edition under your windows version if you have it. If it is there, you just need to find the startup icon. On a fresh install from the restore disks, it will have a green windows icon that say "Media Center" under start->all programs. If you have modified your install, you will still have the C:\WINDOWS\EHOME\ehshell.exe to start it up.