If Windows is booting you can just copy them over manually.
If Windows is not booting, you must load the recovery console or some other means of accessing the drive and use a command like:
copy c:\windows\servicepackfiles\I386\filename.sys c:\windows\system32
This assumes the missing file was in the system32 directory and your boot drive is c:
http://support.microsoft.com/?kbid=314058
Besides the recovery console there are methods of booting a copy of Windows or Linux using a "portable" environment such as BartPE
http://www.nu2.nu/pebuilder/
or Puppy Linux which is also capable of giving hard drive access:
http://www.puppyos.com/
These utilities must be created and tested beforehand so you know how to use them.
If you must choose just one, I'd choose BartPE which is a little more windows like in its method of accessing the drive using a file manager.