Open Source Project Managment / Billing System

Question

I'm looking for an Open Source (or at least free) project managment / billing system, nothing teribly fancy but the minimum requirements are along the lines of:

1. Free.
2. Allows me to add mulitple clients.
3. Allows me to track client payments (super basic here I have an accountant for the major stuff) and send automated reminders to pay.
4. Free

It doesn't have to be Open Source but thats always a plus so I can add any other features I decide I need.

Needs to run on windows. (although a server could be either windows(not iis)/*nix)

Answer 1

Try Open Office .Org's Calc (Excel) program.

Answer 2

It probably doesn't exists (not as one product). If I was building them I would separate the two. If it's good for billing, it probably isn't good for PM. If it's good for PM, it probably isn't good for billing.

For the billing, spend $150.00 and buy QuickBooks. For the PM side, it really depends on what you think Project Management is. You could always use something like Gforge, or one of the many bug trackers out there for keeping track of tasks. The rest of it is planning and estimating.