SoftICE is a kernel mode debugger for Microsoft Windows. Crucially, it is designed to run underneath Windows such that the operating system is unaware of its presence. Unlike an application debugger, SoftICE is capable of suspending all operations in Windows when instructed. For driver debugging this is critical due to how hardware is accessed and the kernel of the operating system functions.
Microsoft offers two kernel-mode debuggers, WinDbg and KD, for no charge. However, the full capabilites of WinDbg and KD are available only when two interlinked computers are used. SoftICE therefore is an exceptionally useful tool for difficult driver related development and continues to function well even with Microsoft's latest operating system versions.
Older versions exist for DOS and compatible operating systems. SoftICE was originally produced by a company called NuMega, and was subsequently acquired by Compuware.
SoftICE is also popular as a software cracking tool.
The "ICE" part of the name is an allusion to in-circuit emulator.