KLC Consulting has created a tool to spoof MAC addresses. This can be used for a variety of purposes such as high-availability systems so you can seamlessly put another system online without changing the MAC address. For more information see this site: SMAC FAQ
Sysinternals BgInfo
This fully-configurable program automatically generates desktop backgrounds that include important information about the system including IP addresses, computer name, network adapters, and more.
Sysinternals Ctrl2Cap
This is a kernel-mode driver that demonstrates keyboard input filtering just above the keyboard class driver in order to turn caps-locks into control keys. Filtering at this level allows conversion and hiding of keys before NT even "sees" them. Full source is included. Ctrl2cap also shows how to use NtDisplayString() to print messages to the initialization blue-screen.
Sysinternals FAT32 for Windows NT4
Another first from Sysinternals: a FAT32 file system driver for NT 4.0. Dual booting with Windows 95OSR2 and Windows98 just got more efficient!
Sysinternals Fundelete
This utility expands the NT 4.0 Recycle Bin to catch file deleted from command prompts and within programs, and it comes with full source code. Several powerful device driver techniques, including getting a user's SID within a driver, enumerating a directory's contents, and generating IRPs, are demonstrated in source code available for download.
Sysinternals LDMDump
Dump the contents of the Logical Disk Manager's on-disk database, which describes the partitioning of Windows 2000 Dynamic disks.
Sysinternals NewSID
Learn about the computer SID problem everybody has been talking about and get a free computer SID changer, NewSID, complete with full source code.
Sysinternals NTRecover
Finally, the utility that NT system administrators have been waiting for. With NTRecover you can access a dead x86 NT system's disks from a good system over a serial connection. You can then salvage data off of the drives using native NT commands and utilities. With the write-version you can even run chkdsk on the dead system's drives! The read-only version is freeware.
Sysinternals Locksmith
Locksmith is an add-on program to NTRecover that allows for the changing of passwords on systems where the administrative password has been lost. It works 100% of the time, and if you've forgotten the password to your machine, you can gain entry within minutes using Locksmith.
Sysinternals NTFSCHK
If you dual boot between NT 4 and Windows 2000 then your NTFS drives were upgraded to NTFS v5 and you have had to boot into Windows 2000 to check them. With NTFSCHK you can check your NTFS v5 drives from NT 4.
Sysinternals NTFSDos Pro
Full read/write access to NTFS drives from DOS! Download this free read-only version.
Sysinternals NTFSFlp
Ever wondered why you can't put NTFS on a floppy disk? Find out how and why NT stops you from doing it, and use NTFSFlp to bypass NT's preventative measures and create and access NTFS floppy disks.
Sysinternals NTFS for Windows 98
Yet another first from Sysinternals: a full-blown NTFS file system driver for Windows 95/98!
Sysinternals Remote Recover
Access unbootable systems from across a LAN or WAN. With Remote Recover you can access a dead x86 NT system's disks from a good system over a TCP/IP connection. You can then salvage data off of the drives using native NT commands and utilities. With the write-version you can even chkdsk, format or partition the dead system's drives! The read-only version is freeware.
Sysinternals SDelete
Securely overwrite your sensitive files and cleanse your free space of previously deleted files using this DoD-compliant secure delete program. Complete source code is included.
Sysinternals ShareEnum
Scan file shares on your network and view their security settings to close security holes.
Sysinternals Sync
Force NT to flush all modified file system data to disk, insuring that it will be safe in the face of a crash.
Sysinternals VolumeID
Set volume ids on FAT and NTFS hard drives and floppy disks using this little utility.