OK the easy thing is to fix your internal storage. Probably the seller hard reset/cleared the phone. Often this "loses" the internal storage. It is easy to replace go to
http://www.htc.com/us/SupportDownloa...at=2&dl_id=436 and download the internal storage hotfix and run it on your phone.
Alternatively you can hook your phone back up to the pc via "diskdrive" mode and then right click on the drive via my computer and quick format. To access diskdrive mode first on your phone go to start/settings/connections and click on usb to pc. Check disk drive and keep the box to "ask first" checked so you can access other methods at will.
To sync your phone, backup contacts, etc. install active sync or Windows Mobile Device center (vista pc) to your PC and then connect phone via usb and set to active sync mode. This way you can backup/import contacts and calendar data... as well as do some installs, connect to reg editor etc.
Active sync method of connection to pc gives access to both main drive and internal storage.. diskdrive mode of connection gives access to internal storage only.