Well, my problem is solved.
I turned out that to make it possible for my system to work full speed I needed to
a) reset the BIOS to factory defaults
b) set settings to the same values that were in place before that. :sarc:
I just want to say this: at this moment all I want is a bullwhip and a couple of hours to get medieval on the asses of those in Phoenix Technologies LTD (and those in Toshiba too) responsible for this agony I (and my computer) went through since I installed RTM.
I'm angry beyond belief. I - no, not I, THEY wasted my time and more importantly the time of those good people in Microsoft that have been helping me with this. Resetting the BIOS to factory settings was the idea one of them came up with. I for some curious reason didn't think of doing that all this time. I mean, who would've thought??? I didn't touch the freakin' BIOS at all during the migration from Vista to 7!!!
All my thanks to the marvellous people in Microsft who I will name if I get permission from them to do so.