Buy.com, once a second-rate attempt at online retailing existing in the rather large shadow of Amazon.com and others, today has a new identity.

Founder Scott Blum has put together BuyMusic.com, a site devoted to selling legit downloads of songs much in the same way Apple’s iTunes Music Store has done.

The difference: BuyMusic.com runs on Windows.

He’s not the first, certainly—Blum’s debut will co-exist with download enterprises including the well-regarded Rhapsody, as well as MusicNet, Roxio’s forthcoming PressPlay-driven “new Napster” and a host of smaller players—but his is the first to emulate iTunes explicitly.

BuyMusic.com, launching today, will have about 300,000 songs on tap for prices ranging from 79 cents to $1.49 each. That’s not the only difference compared to the much ballyhooed iTunes, which sells all singles for 99 cents: The usage rules (i.e. what you can do with a downloaded tune) vary from song to song, according to licenses negotiated with the various labels.

iTunes currently runs only on up-to-date Macintosh systems, but promises a Windows version by the end of the year. The simplicity of the current version of Apple’s Music Store is what has hooked many users: The same, rather liberal usage rules apply to everything.

Other heavies, including Amazon, Yahoo, AOL, MSN and Real are also getting set to enter the online music-store fray. BuyMusic’s Blum is counting on gaining an advantage by being there relatively early. We’ll have to wait and see how that plan pans out.