About once a quarter, Microsoft releases a SP (Service Pack). Service Packs contain bug fixes and enhancements. Service Packs are version specific; i.e. SP1 for NT 4.0 should not be applied to NT 3.51. Service Packs are cumulative, SP2 for NT 4.0 contains the fixes in SP1 for NT 4.0. Besides the executable for your platform (Intel, Alpha, Power PC, etc..), symbol files are often available. These are intended for developers who use debugging tools and should not be downloaded. From time to time, pre and post Service Pack files called HOTFIXES are posted to correct a problem that can not wait for the next Service Pack. You may download the Service Packs and hot fixes from Microsoft's FTP site. Always read all the README info available!
At the Microsoft web site, download the PowerToys listed for Windows NT (NT 4.0 and greater). Make sure you get TweakUI.
There are lots a freeware enhancements and additions such as the Distributed File System so spend some time exploring this site.Type freeware and press GO.