No$GBA is known for having issues with the volume of the mic input. You can use any 'My <language> Coach' ROM to test if your mic is recognized by No$, as those have a voice recording and replaying option. Some games (eg Mario and Sonic at the Olympic Games) have sound tests as well, though the actual volume might not be accurate.
What game do you have problems with?
If there is no recording at all, then your mic is not detected by No$. Try changing the device at Control Panel->Sounds and Audio devices (or something similar; I use hungarian Windows)->Audio->Sound Recording.