you can find the solution in the gp4 tweaker readme
PARAMETERS
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GP4 Tweaker has two switched parameters to control and override regular behavior of the program. Parameter codes are NOT case sensitive. These parameters are:
1. Override GP4 folder/path detection
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Usage: GP4TWEAK.EXE /P[=filename]
Force GP4 Tweaker to detect GP4 files in specific directory instead retrieve it from registry. You can create a desktop shortcut for easy access and set the "working folder" into your GP4 directory using "/P" single switch. This is a good solution when you have more than one GP4 game installed in the system. You may also specify GP4 executable path and filename if different than "GP4.EXE". If the path and filename part contains space, enclosed with doublequotes.
These following examples are valid:
/P <- current folder as GP4 folder
/P=GP4V102.EXE <- use current folder and GP4V102.EXE
/P="GP4 Season 2002.exe" <- use current folder and "GP4 Season 2002.exe"
/P=C:\GRANDP~1\GP4_001.EXE <- specify a different folder and filename
/P="c:\grand prix 4\gp4.exe" <- specify a different folder and long filename
These following examples are INVALID:
/P= <- no filename at all
/P=GP4 <- no extension
/P=C:Grand Prix 4.exe <- contain spaces without doublequotes
/P=GP4+SEASON_2002/03.EXE <- contain invalid filename symbols
2. Override GP4 executable file detection
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Usage: GP4TWEAK.EXE /D[=n]
Force GP4 Tweaker to use a lowest or no mechanism to detect valid GP4 executable file. If "/D" switch is used alone, GP4 Tweaker will only detect some GP4.EXE identification bytes to decide either current GP4.EXE is retail version (v1.00) or patch version (v1.02/v9.6). To force GP4 Tweaker assuming the executable file is in a specific version, use additional code numbers as follows:
/D=1 -> Assume GP4 executable file as version 1.00 (retail)
/D=2 -> Assume GP4 executable file as version 1.02 (patch v9.6)
This switch is useful if you have GP4 executable file detection problem when using GP4 Tweaker in normal way.
USE THIS SWITCH WITH CAUTION! If you use code number and you accidentaly specify wrong GP4 executable file, you may corrupting or damaging that file.