I am unable to perform a repair without a CD-ROM drive?

A. A. Performing any repair requires a CD-ROM in the drive, however this was fixed in Service Pack 2 and later

1. Extract the setupdd.sys file from the service pack installation file
   nt4sp3_i /x
   You will then be prompted for an installation directory.
2. Create a new set of the NT installation disks (goto the i386 structure and run winnt32 /ox (if from an NT box) or winnt /ox (if from another OS).
3. Once all 3 disks are created insert disk 2 and replace the file setupdd.sys from service pack 2 (or 3). To do this you will first need to set the file a:\setupdd to writable
   attrib a:\setupdd.sys -r
   Copy the file to the a: drive
   copy <service pack expansion drive and dir>\setupdd.sys a:

You will now be able to boot off of these disks and repair the registry/boot sector without a CD-ROM. Replacing system files without a CD-ROM is detailed in the procedure Q150497 which can be viewed from http://support.microsoft.com/support/