Client today rang up saying that they'd lost all their documents/emails.
Checked their laptop out and sure enough someone who'd been using it while the normal user was away had somehow corrupted the user profile and had the users folder in c:\documents and settings\ deleted, taking with it all applicaton data, outlook datafiles, and their my documents.
Windows provided them with a temporary account under the "owner" username and they copied all their remaining documents not saved in My Documents to the desktop, which was dumped when they shut the computer down and the account was wiped. And no they are not on a domain as they only have two pc's. They also refused to buy backup disks.
So now I get to spend part of my precious weekend trying to recover their data for them.
Then there is another company we do work for which over the past 12 months has ignored every bit of instruction we have given them on the new network that we setup for them, then when things go belly up try to blame us for it happening and wont pay their bills.
At which point we turn off their email and internet access. 
For example: They are setup with a program call ShareOutlook which allows them to share their Outlook callenders and tasks without needing a Windows server. It does this by sending small emails with the changed data to all other users (4). The average time for the emails to be auto deleted by the program when it is finished using them is approx 6 to 10 seconds. If they are deleted before ShareOutlook is done with them then it buggers up.
So naturally they delete them and then blame us when everything goes haywire. We have explained the correct usage at least twenty times and some still don't get it.
Also somehow they think we're to blame for one of their external hardrives used for backing up data failing. It failed because one of them dropped it on the ground causing the external casing to crack and split, damaging the hard drive. They think that taping part of the case bak together is good enough to get it working again.
I just feel like hitting them with various blunt heavy objects untill they realise how completely stupid they are. Hmm that computer case looks like it will do..........
That is by no means the worst of my problems with users.
Why did I get into tech support, why why why why why????????