amd drivers confusion

Hello all,

I'm a bit confused with the AMD drivers.
Here are my system specs : Gigabyte GA-MA790XT-UD4P + Powercolor HD4890 +
Windows 7 64RC.
Here is my question : what drivers I have to install ? Catalyst
(9-8_vista64_win7_64_dd_ccc_wdm_enu.exe) ? Or Catalyst + South Bridge
(9-8_vista32-64_sb.exe) ?
I thought the SB drivers were included in Catalyst but I am not sure.

It's because I've got some problems with this mb :
- I get some rare freezes after Windows 7 boot up sometimes (and I got some
other freezes - maybe 2 or 3 in three months ! - when Windows was running -
but never when using it)
- I had to change my hard disk (Seagate 500GB 7200.12) with a new one (WD
500GB Caviar Black) because the Seagate got unrecoverable errors after some
months, but after that I still got some freezes - I'm just wondering whether
the disk was faulty or it has been caused by something else (I have changed
the SATA cables too)
- I have checked RAM (2x2GB DDR3 OCZ Gold 1333) and other devices but they
seem to work fine...

N.B. : my system is not overclocked. I only forced the ram to work at 667
(x2), and it does not work better at 533. And there is nothing interesting
in the windows system event log...

Thank you for your advices.

Ash