Have you updated Ulead Video Studio 10? I see there are several updates including one to make it Vista compatible (which would make it more Win 7 compatible). If it hasn't been updated that would be the first step, Vista/Windows 7 handles audio differently than XP and that could be an issue.
Ulead System Support Center - VideoStudio Update Packs
Another issue could be your sound
driver, since you upgraded form XP to Windows 7, you need Windows 7 (or in some cases Vista)
drivers.