SQL2008R2 install issues on windows 7 - unable to install setup support files?

I am trying to install the above but am getting the following errors when its attempting to install the setup support files,

This is the first error that occurs during installation of the setup support files

TITLE: Microsoft SQL Server 2008 R2 Setup
------------------------------

The following error has occurred:

The installer has encountered an unexpected error. The error code is 2337. Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0.

Click 'Retry' to retry the failed action, or click 'Cancel' to cancel this action and continue setup.

For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=10.50.1600.1&EvtType=0xDF039760%25401201%25401

This is the second error that occurs after clicking continue in the installer after the first error is generated

TITLE: Microsoft SQL Server 2008 R2 Setup
------------------------------

The following error has occurred:

SQL Server Setup has encountered an error when running a Windows Installer file.

Windows Installer error message: The Windows Installer Service could not be accessed. This can occur if the Windows Installer is not correctly installed. Contact your support personnel for assistance.

Windows Installer file: C:\Users\watto_uk\Desktop\In-Digital\Software\Microsoft\SQL Server 2008 R2\1033_ENU_LP\x64\setup\sqlsupport_msi\SqlSupport.msi
Windows Installer log file: C:\Program Files\Microsoft SQL Server\100\Setup Bootstrap\Log\20110713_205508\SqlSupport_Cpu64_1_ComponentUpdate.log

Click 'Retry' to retry the failed action, or click 'Cancel' to cancel this action and continue setup.

For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=10.50.1600.1&EvtType=0xDC80C325

These errors are generated from an ISO package downloaded from Microsoft. I have also tried using the web platform installer to install the express version instead but the SQL Server Installation fails with that also. The management studio installs fine but not the server. I have checked to make sure that the Windows Installer is started and it is. Cant seem to find an answer for this anywhere as all previous reported issues appear to be related to XP. I did have the express edition installed on the machine previously but uninstalled it to upgrade to the full version, I wish I hadn't now.

Can anyone kindly offer any advice or point me in the right direction to stop me going insane with this?

Any advice will be appreciated.

Update=======================

After digging a bit deeper ive located details of the error from the setup log file, i can also upload the log file if required.

MSI (s) (E8:28) [23:35:18:705]: Assembly Error:The module '%1' was expected to contain  an assembly manifest.
MSI (s) (E8:28) [23:35:18:705]: Note: 1: 1935 2:  3: 0x80131018 4: IStream 5: Commit 6:  
MSI (s) (E8:28) [23:35:18:705]: Note: 1: 2337 2: 0 3:  Microsoft.SqlServer.GridControl.dll 
MSI (s) (E8:28) [23:35:22:869]: Product: Microsoft SQL Server 2008 R2 Setup (English) -- Error 2337. The installer has encountered an unexpected error. The error code is 2337.   Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0.

MSI (s) (E8:28) [23:35:22:916]: Internal Exception during install operation: 0xc0000005 at 0x000007FEE908A23E.
MSI (s) (E8:28) [23:35:22:916]: WER report disabled for silent install.
MSI (s) (E8:28) [23:35:22:932]: Internal MSI error. Installer terminated prematurely.

Error 2337. The installer has encountered an unexpected error. The error code is 2337. Could not close file: Microsoft.SqlServer.GridControl.dll GetLastError: 0.
MSI (s) (E8:28) [23:35:22:932]: MainEngineThread is returning 1603
MSI (s) (E8:58) [23:35:22:932]: RESTART MANAGER: Session closed.
Installer stopped prematurely.
MSI (c) (0C:14) [23:35:22:947]: Decrementing counter to disable shutdown. If counter  >= 0, shutdown will be denied.  Counter after decrement: -1
MSI (c) (0C:14) [23:35:22:947]: MainEngineThread is returning 1601
=== Verbose logging stopped: 13/07/2011  23:35:22 ===

This was due to a corrupt ISO file