QuickBASIC 4.0 is similar to 4.5, except with a less advanced IDE and online help. However, the compiler supposedly has faster math operations (although I have not confirmed this), so it may be useful to some.
See the patches section for additional patches and utilities for this compiler.
Note: QuickBASIC is no longer sold or supported by Microsoft. Therefore, I am making it available for download here. If you represent Microsoft and want this download removed, please contact me.