Some of them are good to know.
View your boot loader settings, such as your default OS and selection timeout, as well as your boot entries and load options.
You probably already guessed that this defrags your hard drive. Type only defrag into your command prompt to get a list of possible arguments, such as the drive letter and the type of output.
Manages your disk partitions. After you type "diskpart" into your command prompt, your prompt will become "DISKPART". Type a question mark to get a list of possible arguments. Type exit to leave diskpart.
Will get you a nice list of your drivers and their properties.
This is a handy command. You can do everything from managing your hardlinks to querying the free space in a volume. Type "fsutil" into your command prompt, and you will see a list of options. I choose "fsinfo" from the list, so I type "fsutil fsinfo" into the prompt. Now I get even more options, but I choose "drives" by typing "fsutil fsinfo drives." It's fun. It's easy. You'll get the hang of it. Explore this utility, there are a lot of cool features and hidden twists.
This gets the MAC (Media Access Control) address.
Get the RSoP, user settings, and computer group policy settings.
A network configuration tool. Type "netsh" to enter the tool, or "netsh /?" to learn more about it. To exit this tool, type "exit" at the "netsh>" prompt.
Allows an administrator to display or disconnect open files in XP professional. Type "openfiles /?" for a list of possible parameters.
This command attempts to recover readable information from a damaged disk. Type "recover" to get the syntax.
The console registry tool. Get syntax help when you type "reg" into the prompt. You can export the registry, copy, restore, compare, and more.
The administrator can schedule, run, change, or delete tasks on a local or remote machine. Type "schtasks /?" without the quotes for a list of options.
The system file checker scans protected system files and replaces the ones you (or your applications) hacked beyond repair with the real, official Microsoft versions. Type sfc into the command prompt to get a list of options.
You can shutdown or restart your own computer, or an administrator can shutdown or restart a remote computer. Type "shutdown" into your command prompt to see a list of possible arguments.
Basic system configuration information, such as the system type, the processor type, your time zone, your virtual memory settings, and much more.
Want to know what's going on behind the scenes? Type "tasklist" into the command prompt and get a list of current processes.
Now that you know what's going on behind the scenes, maybe you want to shut a few of these extraneous tasks down. That's where taskkill comes in. Type "taskkill /?" for a quick lesson in the syntax of the command, then shut down all those random processes. You can kill MS messenger by typing "taskkill /PID 1680." I got the PID from running tasklist, above.
Another one I found recently is the commonly used tasks feature in XP. Every three days (who chose 3 days?), XP moves the important parts of your commonly used applications to faster sections of your hard drive to decrease load times. If you had a long day or two, use the following command to run this:
You should see some disk activity as the system reorders your applications.