Frelyx

Windows 7 sets MTU = 1500 as default which might have some problems with your old gateway device, generally it will have below problems:

1. All ok with network connection, ping ok.
2. Download with FTP ok.
3. Can not open some specific webpage, it looks very slow with your internet connection but you do have high download speed within a ftp connection.

Display MTU under Win7:

net sh interface ipv4 display subinterfaces

Check the MTU with your gateway devices with ping command under Windows 

ping -f -l 1472 gateway_ip_address

If returns a "Packet needs to be fragmented but DF set." which means the MTU of your gateway device smaller than 1472, you may try again to find out the correct MTU and then setup the MTU in your Win 7 system.

To setup the MTU, follow below command:

net sh interfaces ipv4 set subinterfaces “You Connection Name” mtu=correctMTU store=persistent