At first blush, it sounds like you just have a noisy hdd, that you might want to replace, especially since this is a DAW.

What kind of puter is it? How long have you had it? Has this been a problem since you got the thing? Do you only have the one hard drive in it?

Tom

Maybe your machine is low on memory, and "swapping" to disk - meaning that the computer finding itself starved of main memory resorts to using the much slower disk as memory. Can cause some nasty audio glitches as a consequence.

HTH,

Daz.

Do you also hear noise when moving the mouse? Its poor DAW card isolation from the computers powersupply rails allowing spurious noise from connected peripherals back into those same rails that your DAW card is powered from.
This can be attributed to but not limited to:
computer power supply design
motherboard design
DAW card design(inclusion of a power isolation transformer on card is best)
peripheral design (like drives and other motorized stuff)

All the above can come into play here.
You can try :

a better spec'd power supply
a different mobo
different hard drive
Less effective in this particular situation:
a line conditioner
battery backup unit
balanced ac power
star grounding

I've had the best luck by actually modding the DAW card and supplying voltage to it from a pro video wall wart. They really should all have this feature(sharing a 'puter's power supply with a pro audio card has always seemed like a silly idea to me).
There was a guy who powered his DAW card from battery. Now theres some isolation...

Guys,
I upgraded Jim's machine a while back and it was fine for a long time.
Something must have changed since the last time I was there when everything sounded and worked great.
Supposedly this all started when he bought Reason. I would assume that something in that install must have caused this or somehow the settings have changed.

Opus