raj - sounds like you're looking at the speed of your (presumably) wireless connection. 36Mbps and 48Mbps are typical 802.11g wireless connection rates.
This is simply reporting the speed your computer is connecting to the router at. Nothing to do with the actual Internet service. Many people get confused by this, and I can see why.
Virgin's 10Mbps service speed is slower than your internal wireless speed, so that's ok
Like kitz and OF said... try the online speedtest which will tell you how fast the connection is.