Your box is probably just about OK, but it'll need to be in a healthy state.
Rip out (uninstall) anything that you don't need, delete anything off the hard disk that you don't need, and free up as much space as possible. Clean everything up, cache, recycle bin etc. Use disk cleanup. Turn off any antivirus, or anything else that gets started at boot time that is not required to run windows. Run a disk integrity check. Defrag your disk regularly (once a week). Go into task manager and set the CPU priority for MyTheatre to real time. In MT, set up at least a 200MB timeshift buffer in c:\ (root directory) and turn it on.
Make sure that nothing is running on your system that shouldn't be like adware/spyware or trojans etc. Use Adaware and spybot, or anything else you can find to really scrub it up. NSW2K4 or better is a god general tool. Also good for cleaning the registry. A mucky registry can slow down your box a lot.
This kind of stuff usually generates a performance boost for most folks, but if you are also 'decrypting' channels, then you are likely to be at the limit of your machine. My PIII 800 / SS2 worked fine most of the time.
Also make sure it's real cool. SS2 generates a LOT of heat.
Good luck.
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