There are tons of people with the same issue (sound stutters, delays, etc.) on Windows 7 with Realtek on-board sound cards and I have found that simply disabling Windows Defender completely solved my problem.
I have Webroot and Malwarebytes Anti-Malware installed, and had no idea Windows Defender was still running. After suffering from sound stuttering issues for months and months, trying everything from updating drivers to uninstalling drivers to disabling all sorts of crap such as hardware acceleration in Flash, etc., this is the first and only thing that has solved the problem for me.
To turn off Windows Defender, go into Control Panel -> Windows Defender -> Tools -> Options and go through each of the various option panes on the left and uncheck everything.
I've seen other posts talking about disabling Microsoft Security Essentials, which I don’t appear to have installed (or at least not running that I can see), so if you have that and you have another viable anti-virus or anti-malware security app installed, consider disabling it as well.