I've seen threads where people ask about "How fast you can enter a corner etc?".

I would't pretend for a minute that a skilled PC racer is necessarily safe behind the wheel (one might even argue that overconfidence could cause an unsafe event) but there are still lessons you can learn while having a bit of fun.

A good way to safely explore performance driving theory is to get a racing simulator (actually I like Grand Prix Legends - its an old Sierra title you can pick up for $12 on ebay - so old you will need to download some patches) and a wheel for your computer. Now its not at all realistic with respect to FEEL. There's no significant steering feedback even with a force feedback wheel - and you can't feel the car stick or break loose in the seat of your pants - (the best you get is watching the body of the car against the background movement to try to figure that out) - but you do get a shot at the experience to understand corner lines, entry and exit speed, off throttle oversteer, slow in-fast out, etc. And its kind of cool trying to drive those old 60s GP cars - a big missle motor and monster gas tank on rock hard tiny tires. Those guys were real men.

Also the PS2 Gran Turismo 3 (I've never tried it with a wheel - The PS2 controller is no way to even pretend to be driving a car - and so it got old really fast) might be your thing with some actual driving lessons available. They actually have an S2000 simulator that seems to work pretty well.

(I have not tried any of the newer games, I'm kind of "over it" with respect to PC games - a lot of them are too arcade and very unrealistic - maybe some other people could contribute.)

Still nothing beats getting out to a track with some driving lessons, but really understanding the theory first can help make that more productive as well.