Introduction:

This guide tells you step by step how to register the .dll file manually which is required to play Swamp. This works in Windows 7 and 8, both 32 bit and 64 bit. There are a few 64 bit users who can't get this to work by following the guide. sorry, I don't know what you can do there.
There are other ways to do this than I've described here, but I chose to describe it in this way, to make sure you can master it no madder what keyboard layout and language you're using, because the backslash key is placed differently on the different keyboard layouts.

Here is what you have to do:
Copying the dx7vb.dll file:
If you're running Windows 32 bit, you have to copy the dx7vb.dll file into the following folder: c:\windows\system32.
If you're running the 64 bit version, you have to copy the file into: c:\windows\syswow64.

How do I check if I have 32 bit or 64 bit?
That's simple. Locate your C drive, open up the Windows folder and see if you have a folder called Syswow64. If you have this folder, then you're running 64 bit. If you don't have it, you're running 32 bit. Please note that system32 is in both operating systems.

Using the command prompt:
When you have copied the file to the folder, you have to open the command prompt. You need to do this the following way:
1: Find the command prompt in your start menu. In Windows 7 it's in all programs, and in Windows 8, it's somewhere in the programs list.
2: When you've found the prompt, then press shift f10 to right click on it.
3: Arrow down to Run as administrator and press enter.
4: Type: cd.. and then press enter. Remember to press periode twice.
5: Type cd.. again and press enter.
6: type cd windows and press enter.
7: type either cd system32 or cd syswow64 and press enter.
8: type regsvr32 dx7vb.dll and press enter.
You should now get a message telling the file has been registered successfully.
9: Type exit and then press enter to exit the window, and you're done.

I hope that works for you. If not, I hope Aprone can give any advice on what to do.