You could try feeding your HijackThis logfile into the online analyzer at
HijackThis Logfileauswertung
It will mark many items as known to be innocent, some as unknown therefore potentially suspicious and some as known nasties. Then you can Google about the unknown ones. It can save you lots of time investigating items in the logfile.
Freezes which always happen on a particular event, such as always when you start ProgramX or perform a particular function are most likely to be caused by software corruption. Random freezes are likely to be caused by hardware faults such as bad ram.
I suggest you download memtest86+ from here
Memtest86+ - Advanced Memory Diagnostic Tool
It's an iso image file which you burn to make a bootable CD. If you don't have a CD burner such as Nero, this is a good free one:
The Official ImgBurn Website
Boot the memtest CD and run it for a few hours. If it reports an error, try testing the ram sticks one at a time to find the culprit. Even one error reported is not acceptable if you want the random freezes to stop.
Apart from faulty ram chips, you could get memtest errors just from too much overclocking, so you could try setting BIOS defaults for timings.