The items that can trip you up are the idiosyncrasies and utilities you don't interact with that much. While not intended to be inclusive, here is a list of 20 items to make sure you're not thrown by:

1. When it comes to 32- and 64-bits, know that you can run 32-bit software on 64-bit hardware, but you cannot mix 64-bit software with 32-bit hardware. x64 is also referred to as AMD64 since AMD defined the 64-bit instruction set used today.
   
   
2. In Windows 7, the Quick Launch area was replaced with a mechanism where commonly used programs can be pinned to the Task Bar. After Windows XP, the Search option on the Start menu disappeared as well in favor of the Search box directly on the menu. Within that Search box, you can quickly find commands by typing into the field and letting the system display matching commands (or files, or most anything else).
   
   
3. Press Ctrl-Shift-Enter to run a command as Administrator. For example, type CMD into the find field on the Search menu, then press Ctrl-Shift-Enter to run a command window with Administrator privileges (Windows Vista/7  -- partially through the UAC -- discourages the user of administrative privileges other than when system operations are performed.)
   
   
4. There is a key difference between sleep and hibernation. Sleep (often used on laptops) leaves everything in memory, then all other devices except memory are powered down. The time to resume work is almost instantaneous. Hibernation copies everything out of memory to disk and then everything -- including memory -- is powered down. To resume work, the PC is booted but everything is loaded back into memory so you can start where you left off. There is also a hybrid used on desktops that copies everything out of memory then turns everything off except the memory. This means the PC can start very quickly but if power is lost it can do a resume from hibernation back to the state it was in before it went to sleep.
   
   
5. NTFS file names can have multiples of any allowed character in them -- including periods. You are forbidden from using  / \ > < | ? * ; "
   
   
6. Remote Assistance permits people to access this system in response to requests issued by the local user using the Windows Remote Assistance tool. Remote Desktop, on the other hand, permits people to log into the system at any time using the Remote Desktop Connection tool.
   
   
7. Both Windows Vista and Windows 7 use the WinRE recovery environment to do a complete PC Restore to achieve the same goal as Automated System Recovery (ASR) in Windows XP.
   
   
8. There are subtle name changes between OSes as to what they call applets and tools. For example, what Windows XP calls "Performance," Windows Vista calls "Reliability and Performance Monitor" and Windows 7 calls "Performance Monitor." Similarly, OSes from Windows Vista on display -- by default -- a user-friendly screen for the Control Panel. Clicking on Classic View will show all the available Control Panel items. The view that you use makes a difference in how you access the applets.
   
   
9. The default directory for the Windows folder is C:\WINDOWS. On a standard Windows 7 and Windows Vista installation, the /BOOT directory holds the boot file configuration for Windows. Boot logging in Windows XP creates the NTBTLOG.TXT file in the %SYSTEMROOT% folder (usually C:\WINDOWS).
   
   
10. An upgrade preserves the existing applications and user data moving them into the new system. A clean installation either wipes the old system or replaces the existing system putting the old files into the folder WINDOWS.OLD.
    
    
11. Microsoft Windows User State Migration Tool (USMT) allows you to migrate from one OS/machine to another such things as user files settings related to applications, Desktop configuration, and accounts and is intended for large installations and v2.6 required domain controller access, while v3.0 does not (you do need domain controller access to transfer domain accounts). Windows Easy Transfer (WET) is more appropriate for smaller installations. Obviously, if you're doing an in-place upgrade, you don't need either option since user files and applications are preserved. One other key difference between the two is that USMT allows transfers to be scripted whereas WET uses a GUI which requires user interaction.
    
    
12. Windows Anytime Upgrade does not exist in Windows XP, but in Vista/7, it allows you to upgrade from one edition of the operating system to another.
    
    
13. PXE (Preboot Execution Environment) is a mechanism to allow you to boot a PC over the network rather than from a DVD, USB, or hard disk.
    
    
14. The Power User group in Windows 7/Vista has no more rights than a standard user. The group has only been left in the OS in order to provide backward compatibility.
    
    
15. When configuring network settings for a client, you can configure them to obtain an IP address and corresponding values dynamically or enter static values. It is ONLY if values are dynamic that you have the ability to set an Alternate Configuration.
    
    
16. BitLocker encrypts the whole volume and whatever is stored it (whereas EFS encrypts one or more files or folders on a volume). While BitLocker benefits from the Trusted Platform Module (TPM), it doesn't need it. It can also be operated using a USB drive to store the encryption keys.
    
    
17. During installation, selecting for the workstation to join a workgroup has no real implications. Choosing for it to join a domain, however, requires you to provide account authentication to join the computer to the domain.
    
    
18. TASKLIST is used at the command line to see a list of the running processes similar to what you can see in the GUI by using Task Manager. By default, it shows the processes on the current machine, but the /S switch can be used to see the processes on a remote machine. The /SVC switch will show the services hosted in each process and you can use /U if you need to run the command as another user (/P allows you to specify a password to be associated with that user).
    
    
19. TASKKILL is used to terminate processes. Those processes can be identified by either name (/IM) or process ID number (/PID) and the process can exist on the machine where the administrator is sitting (the default) or on another machine -- in which case you signify the other machine by using the /S switch.
    
    
20. In the world of Microsoft solutions to virtualization, Microsoft Virtual PC 2007 for Windows Vista and Windows XP is popular, as is Windows Virtual PC for Windows 7. XP Mode is a free emulator from Microsoft that you can download and it supplies a pre-configured virtual machine which is run in the Windows Virtual PC emulator (the hypervisor).