Chess PC software for training and playing

Hi All,

This is my first posting here, so please bear with me if I breached any ettiquette or have posted this to the wrong location. 

I'm looking for recommendations on chess software for a PC.  In addition to playing against it, I'd also like to be able to use it to help me train/improve my game.  For example, by allowing me to:

- enter in particular positions and see the different variations the software comes up with

- get move recommendations / advice in a given position

- be able to liberally take back moves and try different ideas out

- configure how well the software plays (i.e., be able to tune the level) as well as the playing style of the software.

I'm not sure which packages (e.g., Rybka, Fritz, Shredder, etc.) provide such features. 

In terms of background, I used to play chess actively a couple of decades ago when I was teenager.  My last USCF rating was a little shy of 2000, but I was probably playing at a stronger level (e.g., 2200 or maybe a little less) -- I had stopped playing tournaments (in large part because of the time and money involved), though I was still hanging out at the chess club, playing blitz, and analyzing games, etc. 

I recently got the itch to get back involved with playing chess again, and am looking for computer software to not only be a sparring partner, but to help me improve (or at the very least get back to where I was)!

Thanks in advance for your help!

You can download Chessbase Light for free and check it out. I think you will be able to do most of things you mention.