Yes, the missing NvCpl.dll is associated with your nVidia driver. As you have downloaded a replacement for the corrupted/damaged file, extract it to C:\temp and then move it to C:\windows\system32. You may have the existing file remaining so just click "yes" if you are asked if you want to replace it.
Have a look at the nVidia website for the latest driver for Win2K/XP and search for "stub32i.exe" or "45.23_win2kxp_english_whql". The latest driver will be listed as one of these. Download and install.
I had this problem last week when, after downloading a beta version of "BootSkin", my computer woudn't reboot properly.