Recording sound without a microphone

Hi.

For as long as I had my computer I was able to record my voice (or join voice chats) using just my speakers or plugging in earphones in the earphone socket of the speakers and using them as a microphone. It all worked perfectly.

...until a couple of months ago.
I cannot remember any software change being made on my computer exactly when this happened so I cant link it to some event and work it out from there (although I did try reinstalling a different edition of my sound cards driver - no result).

I right click on the sound icon at the far right of the task bar of windows and select "Recording devices". There, before it all got messed up, one entry (out of the 3) was active, working and picking up sound. Now all 3 are greyed out and have the indication "Not connected" (or whatever the translation is - my OS's language is Greek): 2 "Microphone" entries and one "Line Input".
I did try to search it a bit by right clicking on each on of them and then "Properties" but I dont know what would need fixing (I did try sliding the volume bar to the right - no result either).

I also tried plugging my earphones on the pink socket of the sound card - directly at the back of the PC's case. One of the entries then gets activated but still picks up no sound (either on voice chats or other sites that need sound input). Which means I might have a problem even if I buy a microphone.

The weird thing is this: before I reinstalled a different version of my sound cards driver, I right clicked on the icon in the task bar that lead to the sound card's management menu (no longer exists after the reinstallation...) and pressed "Record sound" (it had that option) and it worked! A very small window appeared with a "record", "stop" etc buttons and I recorded.
But it still wouldnt pick up sound in, say, Steam voice chats, Vocaroo etc

Added info:
OS: Windows Vista Home Premium 32bit Service Pack 2
Sound card: Here when I go to System Info and see my devices it says:
"High Definition Audio Device"
Manufacturer: Microsoft
But my drivers for the sound card always came by the name Realtek unless I am totelly getting this wrong.

 

Sorry for bumping this but I cant find an edit button.

Here is the info about my motherboard with its built in sound card:

Intel® Desktop Board DX58SO:

Intel® High Definition Audio subsystem in the following configuration:

* 10-channel (7.1) Dolby Home Theater* Audio subsystem with five analog audio outputs and two S/PDIF digital audio outputs (coaxial and optical) using the Realtek* ALC889 audio codec

http://www.intel.com/products/desktop/motherboards/DX58SO/DX58SO-overview.htm