I'm trying to restrict my exe to only one at any time. I've used the following code:

Mutex : THandle;

Mutex := CreateMutex(nil,False,'MyMutexName');

I got the following error in CreateMutex:

'Invalid Number of Parameters". How to create a Mutex in Delphi?

AFAIK it should have 3 parameters. If you put the cursor after the first parenthesis, and press ctrl+shift+space, what does it say ?

press ctrl+shift+space

I don't know which editor has this shortcut. Actually I'm using Delphi with Inno Setup.

It's a Delphi IDE shortcut, which version of Delphi are you using ?