PowerBASIC for Windows
PowerBASIC for Windows is an implementation of PowerBASIC.
Other implementations of PowerBASIC.
PowerBASIC for Windows (a.k.a. PB/Win) is the Windows compiler for PowerBASIC. This is the version that is meant to deal with windows, and there is an add-on (called PowerBASIC Forms) that can make this task easier.
It's important to note that there are some fairly major language differences between the DOS and Windows versions of PowerBASIC.
History
PB/Win was originally named PowerBASIC DLL Compiler (PB/DLL), which reflected its original purpose: writing DLLs for Windows, both 16-bit and 32-bit. (Normal applications were supported in a manner similar to other contemporary languages, using resource scripts to draw windows.) With version 7 the name was changed to PB/Win and 16-bit support was dropped.