Maybe, maybe not. Rosewill does not manufacture ANYTHING! They take products built by OEM manufacturer's, slap a Rosewill label on them, then sell them as their own. The model number on that PSU is AP-600X...google it & see what you come up with.
If you look at the specs, it has 50A on the +5v rail. Generally, overloading the amps on the +5v is a trick used to drive up the PSU wattage rating. In reality, that is a 400-450W PSU.
If this PSU is for a socket A AthlonXP system, you certainly don't need 550W. A good 350-400W PSU would be plenty.
http://www.newegg.com/Product/Product.asp?Item=N82E16817103013
http://www.newegg.com/Product/Product.asp?Item=N82E16817104953
