I use Fritz 11. If you set up a game, turn on infinite analysis, set up your position, and turn off infinite analysis, you can play the position with the computer from there, I think.
Rated game vs Fritz using Opening or a position?

IcyLight,
Thank you for your reply. I can play with the computer, yes. But, that is not my full question was. I know we can play a full rated game with fritz (fixing Fritz's rating to anywhere from 1000 to 3000) , which will start from the beginning. But, I wish to play with the (Fritz) computer when the (Fritz) is rated (2000, 1500, or some other rating) at certain position or using the opening training feature.That is my specific question.

I don't really use Chessbase programs any more, but it seems to me that you could just create a new ctg opening book with only one opening in it. (Either the sequence of moves, or just the final position in that opening line.) I suspect the Opening Trainer is just a cbh database of games, each game showing that opening's moves.
I've done something similar to this in Arena, but I've never tried it in any Chessbase program.
Maybe this article will give you some ideas:
http://www.chesscafe.com/text/lopez25.pdf

IcyLight,
Thank you for your reply. I can play with the computer, yes. But, that is not my full question was. I know we can play a full rated game with fritz (fixing Fritz's rating to anywhere from 1000 to 3000) , which will start from the beginning. But, I wish to play with the (Fritz) computer when the (Fritz) is rated (2000, 1500, or some other rating) at certain position or using the opening training feature.That is my specific question.
As to that, I don't know, my apologies.

If you want to use a specific opening, you will need to create an opening book with the opening you want to use. Here is a video that explains how to do it. I believe it also mentions how to set-up Fritz to use a specific opening.
http://www.youtube.com/watch?v=OItKEDdtKak

To set the starting position you can play through the first few moves in infinate analysis mode. Another option is to set the starting position and click on "theme blitz" under the training tab to play games from that position.
To adjust engine strength you need to play against an engine that has an adjustable strength option. Just go to the Engine tab > Change Main Engine > Advanced... > Engine Parameters. In Houdini the option is called Strength (0-100) and in Stockfish it's called Skill level (0-20).

To set the starting position you can play through the first few moves in infinate analysis mode. Another option is to set the starting position and click on "theme blitz" under the training tab to play games from that position.
To adjust engine strength you need to play against an engine that has an adjustable strength option. Just go to the Engine tab > Change Main Engine > Advanced... > Engine Parameters. In Houdini the option is called Strength (0-100) and in Stockfish it's called Skill level (0-20).
Thank you everyone for your replies. Squareshot cleared my doubt. Thank you.
Hi,
I wish to know if we can play a rated game (example, Fritz = 1800 level) against Fritz software for a
1, particular opening (in opening training) or
2, with a particular position set up.
How?
Please let me know, I would appreciate it. I welcome your replies if you are using one of the Deep Fritz 10 to 14 versions. Thank you.