Alright, skip the $10. I just checked Borland's site, and it appears you can download C++ BuilderX just by registering in their system. They ask for you to let them contact you about products, but I believe the version of C++ BuilderX that you download is not just a trial, but infact is a full working copy with the advanced features removed. Just a note... their website and registration system was giving me alot of troubles earlier, but I think this might be because my account was quite old. Hopefully creating a new account is relatively painless.
As for exactly what C++ BuilderX is... I believe it's an update on their C++ Builder 6 that is meant to incorporate their cross-platform code they had developed for "Kylix". Kylix was meant to allow C++ Builder (actually mostly Delphi) to work on linux. You should be able to use C++ BuilderX in place of C++ Builder 6, and since the personal edition is a free download, hopefully it's a good start.
Now... As for needing an IDE. I think I misunderstood what you originally wanted to accomplish. I assumed you wanted to create windows GUI applications, which is what you would mostly use C++ Builder or Visual C++ for. If you would just like to learn C++, then by all means, skip the IDE and the complicated mess that is windows programming, get a compiler, and go nuts. Borland offers there compiler for free, and there are other free compilers you can use instead.
Why does the IDE matter? ... well, it's a little complicated. Windows is largely C. Most API calls are all C function calls. The APIs are large and complicated, and not all that pleasant to deal with. In order for you to sit down with just a text editor and a compiler, and be able to write a windows GUI application, you would need to know how windows works internally. How messages are passed, how windows are created and destroyed, etc. It's not really all that pleasent. This is where Visual C++ and C++ Builder come in. Both of these provide their own extensions on top of what's available in the kernel. Visual C++ provides MFC (Microsoft Foundation Classes) that make dealing with UI elements a little easier, and give you handy classes for alot of things. C++ Builder has VCL (Visual Component Library) which provides an assortment of things, similar to MFC. They probably aren't anywhere near equivalent if you look at them as a whole, they share alot of the UI stuff. It's these frameworks integrated with the IDE that make creating windows GUI applications with C++ alot easier. Without them, you need a pretty solid understanding of the way windows works before you can write anything useful. Unfortunately, with them, you need to understand what the frameworks do for you to really write powerful software, but it's atleast a little easier to get started.