Kinda have to agree with Schroff87 - even back in my Win98 days when I tried System Mechanic myself, it had a few rather glaring bugs.
Hmm, the link refers to the Windows XP recovery console. Windows 7 handles it a bit differently, you would boot from the DVD and select Repair, then go to the command prompt. There is no pressing 'R' anywhere.
You do need your Windows 7 setup DVD either way...or any other bootable disc that lets you access your installed system offline, for example Hiren's boot CD.