RunAs

RunAs is the built-in way to run a command with different user credentials, i.e. with Administrator privileges if you're running a Limited User account. RunAs is available both from the GUI (right-click on a program and select "Run As...") and from the command line (as RUNAS.EXE).

• For everything you ever wanted to know about RunAs but were afraid to ask, see "RunAs basic (and intermediate) topics" (from Aaron Margosis)
• For some useful RunAs shortcuts, see "RANU: smarter CPL and MSC" (from jaybaz)
• For an explorer shell with low privileges but an admin shortcut, see RunAsAdmin Explorer (from Valery Pryamikov)

Limitations

Ctrl-C doesn't work in a RunAs or MakeMeAdmin command shell - use Ctrl-Break instead (from Aaron Margosis's blog)