Assuming you are talking about an add on sound card and not an on-board one then start by removing the card from the motherboard and clean the contacts with a soft pencil eraser and blow out the slot with a can of compressed air, refit the card.
• Download the latest sound driver for your card and version of windows and save it to the desktop.
• Go into Control Panel and select Add/Remove programs, look for any software related to the sound card and uninstall it.
• Go into Device Manager and locate the sound card, right click on it and select Uninstall.
• Run through this
routine and locate any/all sound drivers and delete them. Do not reboot
, just close all the boxes to get back to the desktop.
• Double click on the driver that you saved to your desktop to install it.
If the drivers still drop out then I would suspect the card is faulty.