Matthewj-
There is no scan-line generation per say. However, the static.mp4 does have a scan-line effect that plays when a snap is null. I doubt this is what you are referring to but you can definitely turn the static effect off under the theme options. The crt and bloom shaders are off by default so that shouldn't be causing a slowdown either. I say this, because the shaders can definitely slow down low end machines. Which is why I turn them off by default.
Anyway, how old of a machine are we talking about here? Is it at least a core duo? I tested an older version of robospin on a raspberry pi2 and it was acceptable.
Also, you might want to make sure there was no virus software or updating going on as well - windows only.