is a "lean" install just the operating system and nothing else? if so you could be missing dedicated drivers included on your recovery disk. recovery disks are a real pain, but not the fault of the computer suppliers. microsoft won't allow them to sell the operating system on a disk of its' own; it must be included as part of a package, so that one is lumbered with a pile of junk software one will never use.
if you have a disk of xp pro, try upgrading. boot as usual, insert the cd in the drive and it will autoplay. opt to setup and it will offer to upgrade. xp does have a huge database of generic drivers.
failing that, try going to the website of the soundcard maker and downloading a driver.
hope it helps
