Hmm,have you got 4x1 of ram [timing problem]also turn off cool & quite or some such in the bios,are you sure that ram has been accepted/tested by Asus for that mobo,as for the hdd it is complimentary to the specs of that mobo,so unless it is failing there should be no problems [I have hdd's that go back to 2003],have you defragged lately..
4850's are not know to overclock that well, and they run hot. If you want to overclock them, you have to get some good case cooling going on.
Next, turn off cool and quiet. It is not supposed to make any difference, and the processor should come up to speed when it needs to. But I am here to tell you, and most others will tell the same thing, it performs a lot better if you turn it off.
And yeah, an old slower drive can really slow things down, especially when you are multitasking. Drives have come a long, long ways in only a couple of years.