Hello and welcome to PC Help Forum.
Do you mean ping as in iinternet?
http://support.microsoft.com/kb/314067
If you do mean this then it could just be the time of day you are using internet it can slow the further you are from ISP exchange,if the area were you live the network of other users increases that are also connected to a BT BB.
You could try this and post results back:
Click on start then scroll and open run,type in the box ipconfig then click ok.
Then type: ping yahoo.com.thats ping with a space then yahoo.com
Let me know the results please.