3.51 should be a standard part of Windows 7, but may not be turned on.
go to
Start
Control Panel
Programs and Features
Turn Windows Feature on and off
Scroll and select .Net Framework 3.51
will require a re boot
If it's not there, download here:
https://www.microsoft.com/en-au/down....aspx?id=25150
3.51 and 4 can coexist. Some older programs require 3.51.
for further info see here:
http://www.techhit.com/how-to/instal....5.1/windows7/
hope this helps
Gary