MASM:

WinMain proc

  LOCAL acDriverPath[MAX_PATH]:CHAR

  push eax
  invoke GetFullPathName, $CTA0("driver.sys"),sizeof acDriverPath,addr acDriverPath, esp
  pop eax
start endp


FASM: (то что у меня получилось)

DriverName db 'driver.sys',0

proc WinMain apientry
locals
    acDriverPath db MAX_PATH dup ?
endl

push eax
invoke GetFullPathName,DriverName,sizeof.acDriverPath,[acDriverPath],esp
pop eax

endp