Question : how do you mount a mail store

I'm very new to exchange server.  Our exchange server is on our server...we only have one server.  I made the mistake of uninstalling and reinstalling iis and now our shared calendars are not working.  The message I'm seeing is that I need to mount and mailstore.  Someone please tell me how to do this....if you tell me to use a program please also tell me where that program is.

Thanks

Answer : how do you mount a mail store

Thanks for NOTHING experts!!!!  I ended up having to reformat that server....talk about a few hours I didn't have to spare.  I guess I should give the point to myself.