So for me, one time I can compile a project in 32 bit and the other time in 64 bit. In that case it is handy to have them (both 32 and 64 bit dlls) in the appropriate system directory. Otherwise I keep switching those dlls in and out 
Yes, exactly the latter

Ah well, I've learned a lesson today as well: first check if things work for the bitness of the compiler/IDE itself before attempting anything else.
I really had the impression that user JLWest was compiling for 32-bit, but that turned out not to be the case

In his defence (as well as mine), it is rather confusing especially for newbies. Compiler/IDE is 64 bit, Widget set named "win32", target specific option "win 32 gui application", target OS "win32"/"win64", target cpu "i386" / "x86_64" and you are running on a 64 bit processor, not to mention being able to run a 32 bit OS on that as well
