I found out how to get nwnnsscomp working without a NWN installation. nwnnsscomp doesn't actually use an NWN files - it just does a crude check to see if you have NWN installed. This is easy to bypass (with a bit of technical knowhow). Here's how:
1) Create a new txt file. Paste the following into it:
Windows Registry Editor Version 5.00
Change the "D:\\Games\\Jade Empire" to whatever your Jade Empire directory is. Make sure each back-slash is doubled as shown above.
2) Rename this txt file to install.reg, or any other name that ends with the extension reg. Make sure you uncheck "hide extensions for known file types" in Windows Explorer's Tools->Folder Options->View, or else you'd actually be renaming it to install.reg.txt.
3) Right-click this reg file and click Merge. It should ask you have you really want to merge the reg file with the Windows registry - click yes. Then it should inform you that the operation was successful.
4) Create a new txt file in your Jade Empire directory called chitin.key. Again, make sure you uncheck "hide extensions for known file types", or else you'd get chitin.key.txt.
That's it. nwnnsscomp should now work without requiring a NWN installation. Saved me 1.5gb on my puny laptop HD