Thread Problems Recording with Realtek HD sound card plus advice for getting new sound card

Hello,
I just got a computer off the shelf with something called 'Realtek HD' as its sound "card" but it won't allow me to record anything except with a 1/8" mic on the front panel.

I cannot record with Sound Forge - it gives me vague error messages that do not mean anything to me. (Besides that issue, I HATE this Realtek crap - no help files, no instructions for using it.)

I've tried enabling the other line-in options given; "line in" (rear panel) to no avail - it will only get sound from the front panel 1/8" line-in.
I want to record full duplex, but apparently Realtek doesn't allow this - I don't know because there are no help files.


So...I apparently must purchase a proper sound card, and I need advice;

I would like to be able to record multitracks - but no more than 4 at a time. I also want to mix in real time - in other words, manipulate the various FX and levels as I record.
Do I need a breakout box sound card with a multi-track hardware mixer attached? What about using it with Acid Pro 7? Is it possible to control the Acid mixing board in real time with a sound card's hardware mixer? If not Acid, does Cubase allow this?

It's very difficult Googling for information because all I get are advertisements; besides I don't know what I should be asking in the first place!

My computer has a firewire input (or maybe it's a SPDIF - I DON'T KNOW), plus a number of other inputs like 'SMC/xD' 'CF I/II/MD' 'SD/MMC' and 'MS/MS Pro'. What are all these? Again, there was almost NO information in the box when I bought this machine from Best Buy (Gateway).
Thanks for your help!