Before you delete these, do a search in "My Computer" using the search term "i386". Select "View Details" mode. You will now see where all of your i386 folders are located. As long as they are located in your Windows System and System 32 folders, then you are perfectly safe to delete these mysterious folders from your D drive and Desktop etc.
"After you install the .NET Framework 3.5 SP1 in Windows XP or Windows Server 2003, there is an arbitrary folder that is generated in the root of drive C (and sometimes in the D drive and elsewhere). This folder contains two subfolders that are named amd64 and i386. These two subfolders both include the following files:
An example of this folder's arbitrary location and name might be "D:\54c3cdc3c1d136c4c8dcabe077" and containing the i386 and amd64 folders within its contents.
These files were pending to be deleted from the XPSEPSC installation.
To resolve this issue, delete the folder manually."
Perform the same for the amd64 in the search.
Also, before you delete these, make a system restore point:
In Xp: Start Menu > All Programs > Accessories > System Tools > System Restore (pop up window) > Select "Create a System Restore Point"