Right now, I've a Realtek soundcard. Unfortunately, from what I've come to understand, it's a bit disagreeable with any attempts a user may make at recording inline sound - speaker output. Rather inconveniant, considering I've come to want to convert some music files for which there's no compatible software, and to create gameplay videos.
Also unfortunately, I know hardly anything about hardware, and just about nothing to do with soundcards in particular.
So, anyone got any suggestions on what to do about this problem? What concerns I might have when looking for soundcards, websites I could goto for comparisons, what soundcards exist, etc.?

My suggestion : Buy a sound card.

Concerns : Things like sound quality, outputs, the actual slot the card uses, price, decoders, etc.

I would suggest for a decent low price soundcard : http://www.newegg.com/Product/Product.aspx?Item=N82E16829102002

That's my intention. The problem is, I don't know what's available, nor what reasons I might choose one over another.
... wow, it took me ten seconds to summarize all that into two statements, when I was incapable of coming up with anything better than a long paragraph over half an hour in two seperate forum threads. *cries*

I've always managed to make do with onboard audio, but then I've never cared a great deal. I think my mobo has realtek as well, and I haven't had any problems. Like I said though, with onboard audio and $7 speakers, I am not freaked out about sound quality

Do you have Windows Vista? Vista disables and hides the Stereo Mix device by default. If you are using Vista, then right-click the sound icon in the lower right corner and click recording devices. Right-click anywhere in the list of devices and click Show Disabled Devices. After this, Stereo Mix will be visible and you can right-click on it and click enable.

If that isn't the problem, then I have no idea what the problem is.

Well, quality and features aren't of much interest to me, but the problem is that I need to record, and numerous sources claim that RealTek soundcards will have problems with this.

Nope. XP.

I have always been able to record both my mic and line-input with what is to me decent quality. It isn't studio-perfect by any cry, but it satisfies me.