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It should work. LaCie's site has an application that will let you use LS on OS X.

However, it's worth pointing out that LS discs are typically much more expensive than regular blank DVD's and CD's. And the actual LS process is fairly time consuming.

Not to mention that you'll be sacrificing a SATA port on your PowerMac (your current drive is most likely PATA).

If you can live without LS, this should work fine in both of your systems, and costs a little less:
http://www.newegg.com/Product/Product.aspx?Item=N82E16827151151
 
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