c++ - RegisterClass for window class returning "file already exists" error -

at moment trying create blank window part of dll provides behind scenes communication our platform. no other part of dll ever display anything.

currently instantiate window class such:

wndclass wc;  wc.cbclsextra = 0; wc.style = 0; wc.hinstance = hinstance; wc.lpszclassname = "preview"; 

i register class:

if((registerclass(&wc)) == 0) {    dword dwerrornum = getlasterror();    **some logging function here**    return; } 

registering class results in getlasterror() returning 0x57 translates "cannot create file when file exists" horribly cryptic @ best not directly writing files.

is there better way me create simple, blank window, or better way me debug beyond i've done?

error code 0x57 not have files. error_invalid_parameter.

looking @ code, have filled in 4 of ten members of wndclass. fill in rest well, , should fine.