Reporting the same vcomp100 issue, I have also tried installing the previously mentioned package and am using the latest DX/drivers.
However, I do have an old version of dolphin, in the r4000 range that works perfectly, not sure if knowing that can help pinpoint the problem at all.
Despite the advice posted in this and many of the other forums discussing this problem, I'm still getting the vcomp100 error message. The system requirements have all been met and I have both DirectX and VC++ updated, both for a 64 bit system. I know they are current because even when downloaded from the site itself and reloaded onto my computer they both give me messages along the lines of "You have the current version." I have even gone as far as to download the actual vcomp100.dll file and load it into the appropriate place, in my C:\Windows\System32 file, yet it still does not work, and yes, I have restarted the computer to see if that was the problem. I'm trying to run the 7671 version of Dolphin (and before you ask, yes, I am sure it is the download for a 64 bit system) and I've even followed the "Beginner's Guide" video hosted on the site.If it's any help, I run a 64 bit windows vista operating system and I'm using winRAR to extract the files. It would be greatly appreciated if I could get some assistance, thank you for your time.
Try uninstalling the C++ redistributables you have, rebooting, and installing them. And delete the dll file you downloaded. It is more than likely fake or outdated.
This is complete insanity, but it worked. I am eternally grateful to the both of you, thank you, thank you.