Partial renders are not saved unfortunately. Even though you may have a large amount of memory, TG2 is a 32 bit application so it can only use up to a theoretical maximum of 4GB, and in practice this is actually less, around 3.5GB in my tests. Still this is enough for pretty complex scenes, and usually if a memory-related crash occurs, it only closes TG2 (and you will normally see an error message, it won't simply vanish). The fact that you apparently had a blue screen suggests it is something more serious, very possibly related to the overclocking you did, possibly heat-related. Even though it is only a slight overclock, you should definitely have some heat monitoring software and keep an eye on it.
- Oshyan