How do i repair windows Nt from ERD files which are stored in hardisk folder name %SystemRoot%\Repair folder .

if the machine is a domain controller you can build an ERD from another DC and modify the boot.ini file to reflect the down machine's hdd configuration. if the machine is not a dc then just build a repair disk from another workstation (or the cd). -really all you need is the boot.ini (and other startup files, but not the sam) to get the machine started, the \winnt\repair folder also has the sam and some other files that aren't necessary unless you are rebuilding the machine from scratch and it is a dc. in this case you need the erd from another dc (modify the boot.ini to reflect the disk config in the down machine). -build an erd by running rdisk /o from a cmd or 'run' prompt -modify the 'ARC path' for the drive config according to microsofts grand plan: http://support.microsoft.com/default.aspx?scid=kb;en-us;155222

Rdisk /s at a cmd prompt will format a floppy disk and park the repair files as found in the repair folder on the disk. If the repair files are too large I would suggest running rdisk /s not make the floppy and burn the repair files to cdrw. I would not recommend creating a rdisk from another server even if a DC due to differences in hardware. Appling a erd to a different server then what it was created from can toast your server.