iMac G5 PPC memory upgrade

hi everyone!
i have an iMac G5 PPC, and i´m thinking of upgrading the memory to 2.5G (i only have 512m)
i was thinking in a kingston (KTA-IMAC533/2G) some people told m that is a good one compatible, and for a good price.
but i have a friend that could me GIVE me one: a KINGSTON 2GB DDR2 PC5300 667MHZ - KVR667D2N5/2G. he says that there´s no problem using 667mhz when should be 533mhz.
he is a pc geek, not a mac one.
so...what do u think?shall i try this or is there any risk of hurting my 'baby'?
or this is only for intel based macs?

thanks in advance

I would be guided by recommendations from Apple and a quality supplier such as OWC or Crucial.

tx for ur reply harry.
but i´ve quit anyway...i´m buying the kingston with 533 mhz (KTA-IMAC533/2G), i found it in my country and for a good price.