We don't know. There are some 500W PSUs that catch fire after drawing 200W of power, or voltage regulation goes completely out of spec, and hardware can be damaged. Your 500W PSU may be a 200W PSU for all we know.
Chances are you're fine, though. There has to be a model number somewhere. Find the name of the PSU. If it's a Hercules 500W, throw it out the window.