Question : VPN slows internet conection

I have a user who works from home, they use a VPN to connect to our accounting software with terminal services. This was already set up. ( I have no knowledge of VPN's).  They are experiencing some lag & slow internet speeds.  I have run tests on the internet connection if I connect to the internet I can get download speeds of 4mb/s however as soon as I log on to the VPN the internet speed drops to 500 - 600k !!! download (the upload speeds are both 400-500k which is normal . is there any thing I can do to fix / adjust (clutch) the download speed.

Answer : VPN slows internet conection

Also known as split-tunneling. What are you using for a VPN solution. Many VPN clients require configuring at the VPN server/router end, but if you are using a built-in Windows VPN client, you can change this if you wish, keeping in mind there are security considerations. To do so on the client/connecting PC, go to:
control panel | network connections | right click on the VPN/Virtual adapter and choose properties | Networking | TCP/IP -properties | Advanced | General | un-check  "Use default gateway on remote network"