I have a computer service company.  In other words, a company that
offers computer services to users:  such as mainteainance, repairment,
software installation, updates, etc.

I need to find a software, the cheaper the better, and better if it's
free of course, that can help me manage all my clients, the history of
each client with the company (in other words, all the services they
have used in the past), and that allows me to keep the PC
configuration of each client.  I will use it in a Windows XP platform.
 It must have a GUI interface of course :).

Can anybody help me find it?