I have an old legacy application around for which I only have the installer. it doesn't do anything more than uncompress and register itself and his library's.
As i don't have the source-code it gives me a lot of headaches in maintenance problems. In some particular computers (Acer Aspire One with Windows) just do not run.
I would like to extract the files and re-create this installer with NSIS. Is this possible or I'm nuts?
The original installer has been created with Ghost Installer Studio.
If it uses a MSI file, you can use Orca or SuperOrca to get at the stuff packed inside.
You could try using a program that monitors new files being installed and then get the files that were installed from their respective paths.
For instance, I found this in about 10 seconds with Google, there are more programs like it, but I am inexperienced with those available for Windows.
One option is to find a machine that it does run on, and then install some "install guard" software (often called things like Acme Uninstaller). Use this to track what actually gets installed and then copy the relevant files and write your own.
It looks like a lot of hassle to me, and you may be on thin ice with regards to the licence.