I'm not sure if this will work, but you can give it a try.

Check in to Your Profile > Select B-52 Driver > Extended Download Service > Get New Links.

Now before you download it, check the name of the file (by doing a mouse over the Server 1 (USA) download link). If the file is named csb521_1000.exe, then it is the full CS B-52 Driver (you won't need the original csb520_1000.exe). But if it is named csu521_1000.exe, then it is the upgrade version and you do need the original csb520_1000.exe file.

I bought the B-52 BUFF Exterior and then the B-52 Driver Upgrade, when the B-52 Driver was released, but I ran into install trouble and so I needed to get a new link to download the B-52 Driver Upgrade, but instead of that getting that (csu521_1000.exe), I found that I gotten the B-52 Driver FULL version (csb521_1000.exe) and so I just install that now. It is much easier than installing the exterior followed by the upgrade.

Hope this helps.

Mark