I would agree in part with Bill that RealBand is not really a Daw, though it has some DAW features, but it is a good start to learning the process and its dead easy to get tracks together. C
reating orignal work where YOU want to control every drum hit, every bass line is not what its meant for.

Try KVR (website) for freebie DAWs if you find BIAB or RB limiting.

Real Band and BIAB are still fantastic though - I use BIAB more than anything else, unfortunately I can get RB working at all on my 64 bit system.
Be aware there that there are some areas of the handling of VST (virtual instruments) that really need updating and BIAB wont work with any VST.
Also setting up sound can be very strange, as they are still using (very) basic windows drivers for some tasks/set ups (where the world has moved on decades ago) although PG support is very good ( instant on line customer support). As i say, I cannot get RB working here at all - PG blame my sound card driver, but its a very upmarket sound device with no problems with other apps. There is a thirty day money back gauruntee though.

I feel both very dissappointed that PG have not provided proper sound card and VST support, and absolutely delighted with BIAB's flexibility and the authenticity of its RealTracks technology. I have got BIOAB working after a fashion and can platy along with a track but not record - using my piano VST. This alone is worth the moeny to me. Real Tracks are a huge leap forward from any other accompaniment program

Concerning the other question

With a basic sound card you will probably be limited to one (or perhaps two) mike inputs at a time. There is a difference in gain between instrument and mic inputs.

A keyboard can act as a MIDI dievice or you can input the audio out from the sound that the Keyboard is making - two different things. Think of a MIDI as a 'score', it makes no sound in itself, but it can instruct others (PCS) how to make a sound - just lioke a shhet of music. MID contains more info than a score and it related directly to the copmputer, without you having to see tghe notes. Hit a key and a 'note on' signal goes to hte sound device, take your finger off and a 'note off' signal goes. Ther are many more signals than these. Most people, though certainyl not all, use a keyboard as a MIDI device and keep their actual sound on the computer in the form of a 'virtual insrtument' of some kind.

You can use a mixer to input more than one mike simultaneously, this works after a fashion, but the signals are recorded as a whole so there are no ways to edit a particular sound.

DV247 is a good source of advice rfe particualr products