For 32 bit and 64 bit license is same.At the time of licensing the client may be 32 bit or 64 bit.It is irrelevant.Only number of PCs which you are gong to install SEP is important.In other words there is no separate license for 64 bit and 32 bit.Both are same in therms of license.
If you download the software using any license you will get both 32 bit and 64 bit installation package .....
You can use 64 bit package for installing in the systems with 64 bit os and 32 bit installation package in the systems with 32 bit os
The latest version RU6MP1(11.0.6100) will work with windows vista also.It also works with windows 2000/xp/2003/2008 and with windows 7