Hit Ctrl+Esc and then R, or WinKey+R to bring up the Run box... then type %SystemRoot%\system32\restore\rstrui.exe, and click OK. You can also access the System Restore tool from the Safe Mode command prompt. Boot to the Advanced Options menu (by hitting the F8 key directly after POST), and select "Safe Mode with a command prompt" | Log on to your computer with an administrator account, or with an account that has administrative priveleges | Type the following command at the prompt, and then press ENTER...
%systemroot%\system32\restore\rstrui.exe
... then just follow the instructions that appear on the screen. You could also boot to Safe Mode and access the Run box the same way I described above, or in the conventional manner... and type the same command to access the Restore tool.