I am trying to implement a simplest IVR system with asterisk, iv'e installed asteriskwin32 on my windows system.
what i currently have is
A PSTN Connection
56k voice & fax modem.
Do i need anything else (hardware or software) ? will it work ?
What i need to do for handling multiple calls simultaneously , as i can only have a single call at a time on my PSTN connection ?
You will need some additional hardware to connect your PSTN to the Asterisk box:
http://store.digium.com/boards/
Or you could skip all of that and get yourself a SIP provider, which would require no hardware, just some configuration.
If you want to stick with PSTN, you will need additional PSTN lines for simultaneous calls. With a SIP provider you can get as many "lines" as you want to pay for with just one SIP connection configured.
I'd also like to recommend you get this set up on a Linux box instead, if at all possible. Best of luck, hope you get it setup to your liking!
Oh, and here is a list of many SIP trunk providers:
