Imac 27" problem with windows!

[Eyecon]

I have Mac OS X Version 10.6.4:

Model Name: iMac
Model Identifier: iMac11,1
Processor Name: Intel Core i5
Processor Speed: 2.66 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 4 GB
Chipset Model: ATI Radeon HD 4850
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
VRAM (Total): 512 MB
Vendor: ATI (0x1002)
Device ID: 0x944a
Revision ID: 0x0000
ROM Revision: 113-B9110C-425
EFI Driver Version: 01.00.383
Displays:
iMac:
Resolution: 2560 x 1440
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Built-In: Yes
Connection Type: DisplayPort
Display Connector:
Status: No Display Connected



I installed windows 7 with bootcamp successfully, installed the drivers from the "Mac OS X Install DVD" but i get freeze screens/black screens and a message, "display driver is not responding and has stopped working" when it works again. This happens very often maybe every 5 minutes, sometimes it never recovers from the freeze/black screen and i have to restart from the power button. When he's in a good mood he gives me a blue screen for a change and restarts.
Also i cant access my hard drives because i cant operate as the administrator and it doesn't ask me for a password or something. How do i log in as admin?

 

[chscag]

Moved to correct forum.

You need to go to the ATI site and download the mobility drivers for your 4850 GPU. The iMac is actually a notebook computer built vertically as an all in one machine. The correct drivers will install OK and should eliminate the freezing and black screens.