i have a soundblaster live digital 5.1 and it was a pain in the bum to install but once working its a good wee card.this is the only way i could disable my onboard and get the SBlive 5.1 to work.
check in device manager if your onboard is listed,right click it the select properties/device usage and select "do not use disable" and restart the computer.
enter your bios straight away click here for popular keys to press to enter the bios(it will say on the post screen anyway something like "press F2 to enter set up" or similar but you need to be quick)
once in the bios(every bios is different) check in the advanced or periferal set up menu maybe and look for any reference onboard sound and set to disabled. save and exit.
windows should find the soundblaster 5.1 ok and prompt to install the drivers.click cancel.
insert your driver cdrom and open control panel/add hardware wizard.click next,tell it the hardware is already connected the scroll to the bottom of the list and select "add a new hardware device" then select "install hardware manually"(advanced) select "sound video and game controllers" click next and then click "have disk" and point it to the driver cdrom to install the drivers and playcentre etc.
any problems with it after install and if using drivers that are downloaded,first of identify your exact model no. click here(5.1 live digital should be SB0 220) and then read click here may come in useful.