There is a brand on it, if it is legal. Take it out and look at the back.
450 watts is ample for most computer demands.
All power supplies, by law, in the USA and most European countries require posting of the output for fire and safety reasons. Fines are pretty huge for resellers if that info is not posted on one side of the PSU... and their fire insurance and business license are at risk.
As a general rule, power supplies are ok if they work until you get into gaming or photo design work.
When they quit and stay quit, you need a replacement
If you have a crummy power supply, you are pushing it with the equipment you describe... but we would be more concerned about cooling and power if we knew what uses you were putting to the system.