Besides the obvious that most people use the latter which are faster for running applications.

Would it make sense to have a secondary storage drive as a slower 5400rpm?

i'm interested in the difference in spindle whining noise and with 2 HDDs in a case it might make more sense to keep the whining noise down to minimal.

These are the stats for WD Caviar 120GB

5400 rpm:
Idle Mode - 34 dBA (average)
Seek Mode 0 - 37 dBA (average)
Seek Mode 3 - 34 dBA (average)

7200 rpm:
Idle Mode - 35 dBA (average)
Seek Mode 0 - 39 dBA (average)
Seek Mode 3 - 37 dBA (average)

I'm no audio expert, so I won't try to draw any conclusions from these. Maybe someone smarter will.

Well i do know that ~28dB is average room levels and from those stats i can only conclude that the 5400rpm is still quieter by 1 dB at full seek mode then 7200rpm at idle.

I've got one of those WD 80Gb 7,200rpm drives and i don't even hear any noise from the drive... Silent as a errrm flea??

maybe i just need a more recent drive for storage as the 15gb is not cutting the mustard as is a few yrs old.

You mean 5400rpm, naturally

I believe faster HDD are getting quiter...i can;t hear anything when my 80GB WD Caviar 7200rpm seeks...but what 's really annnoying is that when my 1.5 GB WD Caviar seeks, its pretty noisy with the screeching sound

My WD800JB is absolutely silent. I cannot hear it at all.
If you have any fans on your computer, there's no way you'll hear it.

It also helps that it is amazingly fast as well. It's an amazing drive.

My 20gig 5400rpm Seagate is so much noisier.....in comparison.

I think older slower drives are noisier then some newer faster drive

so in terms of my original question, i think buying a slower but new 5400rpm 40gb drive purely for storage, that means, rarely for running apps off of would be OK and cheaper.

After all, who needs fast storage only space. Noise will even less of an issue.

Awhile ago when I only had a 10GB WD 7200RPM drive, I bought a 20GB Seagate 5400RPM for just storage of big stuff. It was like $120, which was the most I could afford. I was in love with it!

I do not regret the choice, I still have both drives and they're great!

So to your question, I'd say yes. Because 5400RPM drives are cheaper. Price is the only thing I'd agree with however. I believe that 7200RPM is worth the performance increase, but if you're into budget stuff, 5400RPM is great!

The 5400RPM is in another machine of mine - and it has 2 fans in it. Still can't hear the HDD.

heck, i wouldn't even mind a 4200rpm drive if it made a nice difference to the price. I don't believe HDDs in general cater for different levels of user say like the GFX card companies do.

Because most newer drives are faster, quieter, bigger etc, i tend to use my newest one for Windows, Apps etc and my older for Backup, Storage etc... Then when i buy another new one the previous new one becomes the Backup, Storage etc...
Am i making sense????

yeah, my 15gb drive used to be my primary and orginally cost twice what the 40gb costs which now costs half as much as an 80gb.