During the time it's obviously clear that internet is he best way to search and look around about software for Hams. It's also possible to work with an older computer with digital modes. I used for instance an Asus EEE-PC4G for the digital modes. The software on this netbook what runs very well is FLDIGI and MixW32. FLDIGI is originally designed for Linux, but there is also a Windows version. On my Asus netbook runs that great, and it is freeware. There is also a possibility to connect the transceiver via a CAT-port. Then it's possible to control the transceiver via FLDIGI. For that option you have to use the freeware Rig-driver called OMNIRIG.
Look at the websites to read and download the software.

FLDIGI        :  http://www.w1hkj.com/index.htm

OmniRig        :  http://www.dxatlas.com/omnirig/

One of the most complete software programs for operating a Ham Radio station is in mine opinion Ham Radio de Luxe from Simon Brown (HB9DRV). It is a complete software package for all kind of activities within our hobby.
Transceiver control,
Digital modes communication,
Satellite tracking,
Logbook (complete new version 5.0),
Cluster control etc. etc

You can download the a beta version of 5 at the following adres:
Now (begin 2012) there was an forum message wich say thah Simon stopt with further development of HRD and DM780. But good news,  Rick W4PC, Randy KCBH, and Mike WA6PIE bought it and continue HRD and DM780. For registerd users even with support via telephone. See there website at 
http://www.ham-radio-deluxe.com/HRDv5/tabid/139/Default.aspx