As an IT professional, I am sure that you must be having your favorite set of must-have software which you cannot do without. Here is my list of some software I think an IT Pro must have at all times.
Must-have software & tools for Windows IT Professionals
Ultimate Boot CD
Ultimate Boot CD assembles over 100 PC hardware diagnosis tools into one bootable CD to analyze and repair hard drives and boot problems.
Linux Live CD
Linux Live CD is a CD or DVD containing a bootable computer operating system. Live CDs are unique in that they have the ability to run a complete, modern operating system on a computer lacking mutable secondary storage, such as a hard disk drive. Live USB flash drives are similar to live CDs, but often have the added functionality of automatically and transparently writing changes back to their bootable medium.
The Sysinternals Troubleshooting Utilities have been rolled up into a single Suite of tools. This file contains the individual troubleshooting tools and help files. You could read more on this here.
Nirsoft utilities are unique collection of freeware desktop utilities, system utilities, password recovery tools, components, and free source code examples.
NirLauncher is a package of more than 100 portable freeware utilities for Windows, all of them developed for NirSoft Web site during the last few years. You can now even integrate SysInternal Tools with NirSoft Ultilities. More on this here.
Paragon Rescue Kit Free Edition
Paragon Rescue Kit professionally fixes boot problems as well as retrieves your data when your system fails to boot. It even rescues deleted partitions. All you need to do to achieve complete control over any situation is burn the software on your CD/DVD. In case of a system malfunction, caused either by a virus attack or file corruption, you can retrieve valuable information from your disks and copy it to another local drive, partition or save the data to CD/DVD. The File Transfer Wizard helps you to export data as easy and convenient as possible. Details here.
Take a look at Windows System Control Center too.
Have any more suggestions for inclusion? Do share in the comments.