|When you say system restore you mean Microsoft's restore to previous and not the Dell Restore?? |
It isn't easy but look at a few things first. See event logs. See taskman and might have to setup a perfmon (many settings are possible) to view what is causing it.
Worse comes to worse restore it to factory state. It would be good to learn how to do that while you don't have a lot of data on it.
Playing to the angels
Les Paul (1915-2009)