On a wider note - how does everyone else cope with asset management? We have NOTHING at the moment. Someone kept an access database of machines a while ago but it's useless. I have set up Systems Center Config Manager which helps - but only if active directory is free of clutter and the machine sits on the network periodically!
Setup SCCM functionality for internet based client management?
Means you can manage clients (patches etc) no matter what connection they are using, i.e. not on your domain, over any web connection.
Personally I don't and wouldn't use SCCM as my asset register/CMDB, it's too faffy to add in all the extra info. I use it purely for management of the assets, not for storing the records/information on them.
I'm assuming the problem is with them being off your domain you have no visibility or management? If not that, then in a way why do you care if they don't touch your domain for x days?
tbh it all sounds a bit of a mess, asset management is bread and butter stuff and if your place aren't even doing that I'd be worried. I'm guessing your not subject to 'proper' external audits often? (the joys of working for government)
Going by ITIL type stuff you should have a config database which contains your assets. For instance each item will have a unique asset tag, and certain details will be attached to that tag. You'd have what it is (make/model/serial number etc), where it is, who has it, how much did it cost, when was it bought, that kind of thing.
It could be just an excel spread sheet with all the info in, it could be a full on asset management/service desk tool, doesn't matter. The important thing is that you have the information.
I shudder to think what your software asset management (SAM) is like, however I am available at very unreasonable rates
*edit* just found this which has some info for you to look at
http://www.itil-itsm-world.com/itil-1.htm