Well I use shareware Windows Scheduler 3.2.1 and build a cmd file with the command line command to launch silktest and execute my .t or other runable silk files.
See http://www.splinterware.com for the software. Also see Starting SilkTest from the command line from SilkTest's help to learn how to use the command line commands in silk.
I have the Windows Scheduler set to launch the cmd file a set times.
By the way there is a command line command to close silk after the run. You might want to use it if your going to run every two hours. It will help clean up any problems that might occur and the command line command opens silktest before the run.
In NT, you can use the AT command to have pretty much anything run from the command line "at" a specified time, hence the name, "AT." If you prefer it, there is a GUI for this command line program called WinAT. I use this pretty regularly.