Can't install driver for my ATI Radeon 9800 XT VGA card!

Question

Hello:
I own a computer with these specs:
    Operating System                                  Microsoft Windows XP Professional 5.1.2600 (WinXP Retail)
    Computer:
      Computer Type                                     ACPI Uniprocessor PC
      Operating System                                  Microsoft Windows XP Professional
      OS Service Pack                                   Service Pack 3
      Internet Explorer                                   7.0.5730.11 (IE 7.0)
      DirectX                                               4.09.00.0904 (DirectX 9.0c)
    Motherboard:
      CPU Type                                              Intel Pentium 4, 2400 MHz (18 x 133)
      Motherboard Name                                  MSI 845E Max (MS-6566E)  (6 PCI, 1 AGP, 1 CNR, 2 DDR DIMM)
      Motherboard Chipset                               Intel Brookdale i845E
      System Memory                                      512 MB  (PC2100 DDR SDRAM)
      DIMM1                                                  256 MB PC2100 DDR SDRAM  (2.5-3-3-6 @ 133 MHz)  (2.0-2-2-5 @ 100 MHz)
      DIMM2                                                  256 MB PC2100 DDR SDRAM  (2.5-3-3-6 @ 133 MHz)  (2.0-2-2-5 @ 100 MHz)
      BIOS Type                                            AMI (09/13/04)
      Communication Port                                Communications Port (COM1)
      Communication Port                                Communications Port (COM2)
      Communication Port                                ECP Printer Port (LPT1)
    Display:
      Video Adapter                                     RADEON 9800 XT - Secondary  (256 MB)
      Video Adapter                                     RADEON 9800 XT - Secondary  (256 MB)
      3D Accelerator                                    ATI Radeon 9800 XT (R360)
      Monitor                                              LG F900B  [19" CRT]  (121137790)
    Multimedia:
      Audio Adapter                                     Realtek ALC650 @ Intel 82801DB ICH4 - AC'97 Audio Controller [A-1]
    Storage:
      IDE Controller                                     Intel(R) 82801DB Ultra ATA Storage Controller - 24CB
      Floppy Drive                                       Floppy disk drive
      Disk Drive                                          IC35L060AVV207-0  (60 GB, 7200 RPM, Ultra-ATA/100)
      Optical Drive                                      SAMSUNG CD-R/RW SW-252S  (52x/32x/52x CD-RW)
      Optical Drive                                      TEAC DVD+RW DV-W58E  (DVD:8x/4x/12x, CD:32x/16x/40x DVD+RW)
      SMART Hard Disks Status                     OK
I just replaced my old graphics card NVIDIA GeForce2 MX/MX 400 with another old model card, ATI Radeon 9800 XT. Everything was fine until I tried to update a recent ATI driver after uninstalling my old Nvidia driver with DriverCleaner Pro. I get this error message:
  "Setup failed to launch installation engine: Class not registered"
Then, tried to install the driver through device manager with the update driver option. I directed to the driver folder on my desktop and the driver update went through, smoothly. However, when I put my computer in standby mode and then restore to full operation
I got a BSOD with this error msg.:
ati2dvag.dll-Address BF039614 base at BF012000, DateStamp 49344e53
Now I can't use standby mode because the computer just shuts down instead of operating in standby.
Is there any idea why my new card is not being fully accepted in my OS and how can I fix this issue. BTW, my ATI card is an 8x speed and my AGP slot supports a max of 4x speed, but I think my card is reverse compatible with 4x slot with the same voltage (1.5V).

Answer 1

Thank you BOSS for your quick response:
I took your advice and reinstalled my OS, but unfortunately stand-by mode is still causing errors. The only difference is that I managed to install the ATI driver normally and no BSOD, so far.
I'm not sure what is causing this, but my humble guess would be that my ATI card is an OEM card which is pulled form a working dell computer and these cards sometimes do not integrate well when installed on non dell motherboards... However, I need to find out that that is absolutely the case before I remove my vid. card from my system
There is a memory dump file that contains the info about this error but I can't decipher...I'm not a computer savvy, but you or someone here my find the root of the problem in that file. If that will be of any help to provide you with I will, next time.
Thanks in advance!!!