Audacity software worked ok y'day, now no sound getting thru to it. Realtek seems the problem. Why?

[Hell_Bent]

Running a CQ3420AN desktop with 64 bit Win 7 with Realtek Audio  version 6.0.1.6132 installed. Had it from new , now 3 months. Used to crash continuously with AVG anti-virus (bluescreen), replaced that with MSE and all good. For some time Ive been using Audacity software to record and process sound , i.e. convert cassette to mp3, splice etc using a purpose built cassette player with USB connection to front of tower. Has worked fine for ages until today, now feedback, and cant get the sound (which is leaving the player fine) into the PC. It will neither play thru the PC nor get thru to the Audacity software. I changed nothing knowingly, settings wise, just woke up to it not working today. Seems that on Audacity site forums there are dozens of people saying they have various problems, in a particular thread, with Realtek as its controls are often not visible immediately, its settings are defaulted to be negative towards the requirements of that popular widely used software (Aud.). I have now tried every combination of Realtek settings in an effort to remedy the situation, and after that downloaded the latest version of Audacity, which I may add is very sweet. Upon going in depth into the Realtek manual today I find their illustrations and instructions are for a much more advanced version of the Realtek HD Audio manager than that which is fitted to my computer, thus proving useless to me as half the dials and knobs as such are not to be found on my version. I find the folks posting about the problem in the forum I mentioned have a variety of other versions also widely varying from my own Realtek.
1. How am I supposed to utilize the half assed version of Realtek I,ve been supplied with in my new computer?
2. Has anybody got any knowledge of how to upgrade Realtek to the latest version, or a better one, as the manual I was supplied with implies I ought to have received with my PC?
3 Anybody have a solution to make appear any possibly "hidden" controls for HD Audio Manager, which am in process of re-downloading via here (HP) the original driver for, at what appears to be an incredibly snail like pace, an hour for sixty something MB !!!