help: (DVD-RW) or (CDRW+DVDROM)?

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Hi,
I wan't buy a optical disk device for backup. options with me are:
1)CDRW+DVDROM (combo), or 2)DVD RW.
What worries me is that the DVD formats are fast updating (Heard of
the Blue Ray, HD etc). I dont want to see my H/W need upgradation very
soon. My question is, how soon and how badly is the Technology
upgradation going to render a DVD RW obsolete.
If it is very soon, I'll go for the CDRW+DVDROM combo. Are there any
issues here? Thanking you for your comments,
B Sharma

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