Free and useful Windows programming tools

Unlocker will solve the "file already in use" problems for you. Install with only assistant option, no ebay icons.

Dependency Walker will tell you what dependencies are on a program/dll. This can quickly show you which DLLs your program depends on to function.

Inspect Exe show you the export symbols by simply right clicking and selecting properties on any dll files. Very useful do find out if you have properly exported a symbol or even if you have the right version of a DLL.