This thread is 5 years old. Many carriers these days now allow for backup of contacts from the phone to their storage. This makes it easier for restoring them if you have to replace your phone with a new model
Here's a link to Verizon's version of backup assistant
ATT has mobile back up.
Check with your carrier.
If you still want to back up to your personal computer, check out datapilot software or something similar.
As was already suggested, you can use bitpim, which I believe is free. Your phone isn't specifically listed as being supported but the 8300 is.