No sound device

Hello,
Awhile back I had to take my computer in for some repair. These people didn't load sound device on the thing so I've just been doing without it. Now, I have tons of videos of my grandchildren and can't download them on cd's to save as it says no sound device! I'm thinking about just taking this thing in to someone else and getting this all corrected. I'm not computer savvy and it's driving me nuts! I don't trust these pay to use driver updates and such. I've tried everything I know to fix sound through Windows and nothing works as I always get messages such as can't complete,etc. I have Windows XP but a new motherboard was installed and nothing works..thanks!