how to create a new AVD in eclipse?

May be the following will help :

Then start the emulator

Try to create an AVD with the monitor.bat in the tools-folder, that worked out for me!

They most probably have changed some AVD settings. As for your second question regarding what options you should select: Don't make a very tiny SD card. Anything above 100mb should work fine. As for target choose the android version you've downloaded a system image for using the SDK.

I don't understand what you mean by "not be available", but if its the OK button its because you have no target platform.

If you mean, that the emulator won't start up, give it some time. You can even put the emulator in snapshot mode so it will open right where it last left off, saving you time.