It will only do that if the power savings in windows is set to do that.
But it will only vary speeds when its not in full use, or its internal temp is over 50°C.
WD's are nice drives don't worry about it.
There is also no delay in finding data no matter the size, depends on how bad a file is fragmented though, hence why I always say to people at least once per month defragment your HDD/s over night.
This is how files work on a HDD, the header of a file is stored in the inner ring of a plated HDD, the header contains information on the location of the data on a HDD, the size, type etc
So when accessing a file windows will read the header first get the file locations (data can be spread into different areas if heavily fragmented) and then locates that data.
It also depends on your system set up, if the drive is in IDE mode it will be slower than AHCI mode and in turn be slower compared to a Raid 0 or 1+0.
[Edited by DABhand, 3/29/2013 4:25:17 AM]
thanks for the info, about AHCI and RAID i'm learning it right now in mcse(very intersting), anyway the price difference between WD 1TB TO 2TB is about 25$ i think it's quite worth it so i guess i'll go for the 2TB.. what do you think?
and do you think seagate and WD are at the same level quality and reliability wise?
[Edited by kingkob, 3/29/2013 4:42:42 AM]