Use installserver.exe instead of installserver.rmp. This error kinda common with the patch.
How?
Apply open4all in rompatcher. Get the attached installserver.exe zip. And copy it to C/sys/bin.
Disable installserver patch. And try again, shouldn't be any problem now.
All the best.
P.S, can you update your profile with the phone you using. Believe it or not, it's easier for us to help you when we know the phone you used.