PME Preventive Maintenance & Equipment Software
http://www.cool-ware.com We have used this software for several years, but looks like the price has gone up to $479 for single user.
You might want to check out DBA NG just for tracking PME since it's free to you. From the help file:
The Service & Maintenance module is used to manage the service and maintenance of Assets such as machines, tools, facilities, vehicles, etc. Assets can be internal Assets or Assets you maintain and service on behalf of customers.