Don't make the same mistake I rather naiively did. By using CD-R's for copying music I ended up with CD's all over the place, half of which I didn't want so I decided to splash out on 10 £30 CD-RW Cd's to stop this problem. What happened? I got them home and found that CD-RW's cannot be played in a normal CD player so I'm stuck with 10 totally useless CD's who PC Scrud more than likely won't take back. In my defence, nowhere on the damn box did it say this was the case. A clever bit of TDK marketing methinks.
As far as the speed issue goes, it doesn't matter. Pretty much any disc will work - let your pc do all the thinking.
