I have significant first hand experience with "PGP Desktop Professional 9.0 with Whole Disk Encryption" and can recommend it if WDE is necessary. The driver it uses for hdd access with WDE works well enough to be acceptible in a workstaiton environment. If being used on a laptop, I would recommend at least a 2Ghz dothan or 1.6Ghz yonah core for transparent access; if you have less, you may notice a slight performance hit with disk access intensive applications and slightly longer boot up times.

However, overall, PGP WDE has worked very well in all of my experiences with it, and I do recommend it for you based upon the information you have provided.