Well, you can try a few different drivers. My P5B-Deluxe came with the 4530 drivers on the disc and I had problems with them too.
You can try:
4560
http://drivers.mydrivers.com/download/dir155/d62270.shtml This site is in Chinese, but if you hover your mouse over the links you'll see that its for this driver. It doesn't have DTS, but it does add an equalizer to SoundMax. I've tried this driver on my board and it does work.
4570
http://support.asus.com/download/download.aspx?SLanguage=en-us Go to the P5B-Deluxe section and download the latest driver for that board. It might work with the P5B-E too. I'm not sure why they don't have it posted for the P5B-E.
4580
http://rapidshare.com/files/2634578/Audio_Driver_4580_W2K_XP.rar This one you have to install by using the "update driver" button from Device Manager then browse to the driver downloaded from this link. It, therefore, will not install the SoundMax control panel by itself but you can install that with another driver and then update to this one.
I installed the 4570 drivers from ASUS then manually updated to the 4580 drivers on my system. I don't know if these work for the P5B-E, but it wouldn't hurt to try.