Well, this is just me, but I don't trust HP technicians (or any OEM technicians for that matter) with software. They follow predefined procedures for all problems, and they always blame drivers, and when that doesn't work they ignore you. If it's a hardware problem, I would send it in though while it's still under warranty (If you send it to someone else for hardware troubles, you lose your warranty) and at worst you get a brand new computer with brand new hardware.
My fan is also making noise recently. I've read before that the Pavilion series is not unfamiliar with this issue - the fan can't handle too much if you do something out of the ordinary like booting something that isn't an OS, the fan drivers don't tell the fan to slow down, and it goes crazy until the bearings get loose... What kind of fan is one that breaks itself??? Anyway, I think I have no option but to send my laptop in before the warranty runs out to replace the fan... :sa: (for the third time in under a year) Actually, now that I think about it, there's a setting in the BIOS to have the fan always on fastest. Perhaps I'll look into turning that off...
As far as the freezing, it sounds like a situation as sticky as mine... I never got around to learning about real-time debugging, because I did manage to trace back the problem to hard disk partitioning, which solved the issue. If/when I do get around to it, I'll let you know what I know. In the meantime I suggest thinking again if maybe you did do something different after all - or what normal activity might have caused it? Perhaps it is somehow related to the fan issue?
I get it - the problem with this issue is that it's undiagnosable, right? You may want to try reinstalling Vista clean install/restoring it back to factory state (using migwiz to transfer your documents and/or settings) and see if that solves it...