Upgrade NT server to SP6

I am having problems updating an NT server to SP6 (required or an application upgrade). I downloaded the upgrade to a mapped drive and when I attempt the upgrade and go through the create Uninstall portion, I get the message “an error has occurred copying NTLDR”. I cannot locate the NT SERVER CD (w/ terminal services) for this computer and I’m not sure if bypassing the “create Uninstall” portion would be a wise idea. I see several copies of NTLDR in various folders in C: (with OLD dates 1998, 1999), should I point to the one with the most recent service pack#? Any suggestions?