Itunes + XFi + XP = Clicking annoyances

A friend has an X-Fi Xtreme Music sound card and uses Itunes for his (large, 20,000 files) music library in Windows XP SP2. Recently he has begun to have serious problems with the output, persistent clicking noises through every track (ripped OR downloaded, VBR and CBR) which gets progressively worse the longer his music is playing, eventually getting to a point where the speakers are emitting a high pitched whine and his amp is auto-shutting them down to save them from potential damage! He has a motherboard with an onboard sound card (which is disabled in BIOS)
He has the latest version of Itunes (7.1.1.5) and I am going out there on Sunday night to update his XFi to the latest drivers. Has anyone here any other suggestions as to what it could be?

It sounds like its more likely to be the speakers to be honest. thats the sort of thing mine did before they died. What Make/model are they? I know it sounds stupid but have you checked the speaker cables havent come lose? and the x-fi card is seated correctly? I dont mean to offend but the silliest of things can sometimes be the problem.

yeah, i checked that, changed to a pair of cheapo desktop speakers, same problem. The guy is using very good quality cabling going to a Cambridge Audio amp and B&W speakers.
Thought I had it fixed by changing the pci slot the soundcard was using and cleaning and installing the latest drivers. Worked fine for over a week, but the clicks have started to come back again now :(

try moving the card to a different pci slot. my audigy 2 did this until i moved it and its fine now. move some other card from around it aswell as that might help

I know it's monday now..but does the same happen using the onboard sound?

it did initially, but found that it was a known issue with Realtek onboard sound drivers and when i upgraded the driver to the newest version it removed the problem. If it was up to me, he would just stick to the onboard sound, but he likes to think of himself as an audiophile and so wants the Xfi :)

Hmmm.... not exactly the same setup but i have no problems at all with my Audigy 2 ---> Xmod ---> amp/speakers, using itunes & XP SP2.

3 most likely causes: Driver, cables, speakers.

I agree with staffsmike, if you change back to on-board (as a test, dont panic him!) and rule out your cables & speakers that'll leave card/driver only. I know you said you used to use that, but try it now.

I also have a similar problem...

I have Xifi with an Abit motherboard and Creative Megaworks speakers.

I like to use the Digital out, but that causes crackling sounds whenever its on mute, however when I use the normal analog signal its fine.

Its not a huge issue but its annoying at times.