After a few hours of fiddlin', I've finally arrived at a total solution (and moreover, an explanation) for the "unresolved external symbol" difficulty faced when attempting to use Borland's free BCB5.5 compiler through the C::B IDE.
First the problem statement. Even after properly configuring the 2 recommended .cfg files and/or setting up the appropriate global variables inside C::B, people find that when building their projects they receive numerous "unresolved external symbol" errors from the linker, ilink32.exe. When the same file is built from the command-line (with bcc32.exe), the exe is created without issue.
The problem lies with the linker itself. It's flat-out dumb, or at least not as smart as mingw and openwatcom's linkers. Even with the library directories set up properly, the linker requires EXPLICIT naming of needed libraries. When implicitly called from bcc32, the appropriate libs are included. But not when the "Build" command is given inside the IDE. This means that a user must know exactly which libraries are required by the project. As I'm not an expert on libraries (or anything really ^^), I was completely dumbfounded. How the hell am I supposed to know what built-in libraries are needed even by a simple "Hello, World" program? Or even what each library is for? Thankfully, a little research goes a long way.
http://docwiki.embarcadero.com/RADStudio/en/Static_Runtime_Libraries lists all the main libraries included with BCB55 (and more.) A little more searching turned up that all Windows programs must include import32.lib, even console apps. For simple programs, the only other lib needed is cw32.lib, the static runtime library. Thus armed, it is surprisingly easy to get BCB55 to work correctly:
(for C::B 10.05)
Settings > Compiler and Debugger... > (select) Borland C++ Compiler (5.5, 5.82)
under Linker settings tab, add the following to "Link libraries" (order is important according to borland docs):
import32
cw32
That's it. The "Build" command will function as expected provided that the program isn't too complex (uses internet functionality or directx, for example.) If that utility is needed, I'd recommend adding the appropriate library under "Project > Build options...", so as not to include it with every new BCB55 project. The other option, of course, is to simply add the name of every available library in the global settings (this was one of the recommended solutions I found on this forum, but it didn't tell me WHY it was needed.)
While, I'm at it, I'll suggest adding one more thing to the Linker settings. Under "Other linker options" add the text "/x/c/Gn" without quotes. This tells the linker not to generate the extraneous files it normally would.
I hope this helps the few people old-fashioned enough to want to use BCB55 in the first place. ^,^