i have a Intel 510 series SSD 120 GB which I will be running Windows 7 and all my most commonly used programs and games. Now for the HDD i will just use for storage. i am drawn to Western Digital Caviar Blacks because of the 5 year warranty. but should I get 5400rpm or 7200rpm since the drive is only going to be used for storage mostly?
Honestly with hard drive prices so high right now I would go for whatever is cheaper. You might notice a slightly faster access time if you use a performance drive for storage but it's not worth the extra cost with drive prices up at least in my opinion. I have 2 x WD 640Gb Blacks and 2 x WD 250Gb Blues as storage drives and can't really tell a difference when going from one to the other. Everything is so fast on the SSD all the mechanical drives seem slow. The extra warranty on the Blacks is nice but my 250Gb drives are over 5 years old and going strong.
When it comes to storage drives it is more an issue of acoustics than access time. If this is merely a repository for videos and music and such then I would go for whatever is cheap and quiet. The extended warranty is nice, but honestly I have never had a HDD (of any brand) last less than 7 years unless it was DOA to begin with. If you were rendering video, or doing some other 'work' on the drives then I would suggest sticking with the 7200RPM drives, but for the most part the 5400 and 5900rpm drives work just fine for video and audio playback.