I've recently installed the Symbian SDK and the Carbide Express IDE and after some googling around I've just manged to get them working together
My problem: Every time I've started the IDE and went to the Pref/Carbide prefs I got the "SDK not found error" even though I've got the SDK installed.
The solution: It seems that Carbide has a hardcoded path to the devices.xml file --> C:\Program Files\... but my Windows install drive is Ddon't ask why). After symlinking the D:\Program Files\..\Symbian to C: everything worked fine.
Hope this helps.