Toltec, простейший вариант:
Код:

@Echo Off
SetLocal EnableExtensions
Set Copied_1=
If Not Exist %windir%\system32\1.dll (
Copy 1.dll %windir%\system32
Regsvr32 /s %windir%\system32\1.dll
Set Copied_1=1
)
Start /Wait proga.exe
If Defined Copied_1 (
Regsvr32 /u /s %windir%\system32\1.dll
Del /Q %windir%\system32\1.dll
)