2003 server repair install not an option

I have a crashed 2003 server - it wont boot into safe mode and give a blank screen after the widows logo.
I have tried a couple of things such as copying the registry files from backup folder, but in the end it looks like a windows repair install is my only viable solution. However..

I start the windows 2003 install from CD, choose the volume to install to and it prompts "Caution A \windows folder already exists etc" "To delete the existing windows installation in it press L"

I dont want this option - I want the option to repair so it will keep the current windows installation.

My guess is that perhaps I am using the wrong version of win 2003 server CD as I dont have access to whatever was originally used (nor any backup or ASR)

Does anyone have any ideas or perhaps a method that I could find the windows server version somehow from the files on the Hard Drive.  The drive and data are in tact - just wont boot.