Windows print drivers are the bane of many admins and users. These bits of software live in the murky area between the OS kernel and user space, and decisions (and non-decisions) made by their developers can quickly turn a well-running system into complete garbage.
It's my opinion that much of the bad press that Windows gets (compared to Linux or OS X) is the result of poorly coded drivers (and I definitely include video driver in this indictment).
The real head-shaker I'm working on, however, isn't the bad behavior of the driver as much as the peripheral settings and installer that come with the driver.
I ran across a situation where the Lexmark "universal driver" was dropping some entries in the Registry that didn't cause issues in single-user environments, but wrought havoc on multiuser (eg, terminal server) environments.
Specifically, the driver saved a binary value that essentially contained an XML file. On the surface, that would be innocuous, but when the size of the blob is on the order of 500KB—and the same blob is duplicated in several values and keys throughout both the System and User hives—it becomes an issue.
Even when Windows has supposedly fixed the Registry memory restriction and allocation problems, starting in Windows 2003.
Not sure if you have a potential to be bitten by this little gem? Well, if you aren't using Lexmark printers, you should be fine. But if you are, open Regedit and do an exact search for the following value name: GDL
I had a terminal server user with over 50 of these entries in her user profile; when she was logged in, no other users could log on (not enough resources for the registry of the new login). We removed the values, and voila, users could login.
(Of course, I now want away to search for Registry entries by size: anything bigger than 100K needs to be flagged so I can complain to the vendor—even if it's Microsoft—about bloating my Registry.)