find out the iPads IP address
Settings
WiFi
Click on the right arrow beside the wiireless network name that you are connected to
Under the DHCP tab there will be an IP address, something like 192.168.x.xxx
Write it down.
In Windows XP
Start
Run
Type in the box "cmd" (no quotes, short for command) and you will get a DOS box on the screen
at the prompt type (no quotes) ping 192.168.x.xxx (whatever the IPS adddress you wrote down was) and push Enter
You will get a line that says it's pinging then four lines of replies then some statistics.
Basically all you need to see is that you get 4 replies the rest is mumbo jumbo. If you DO NOT get 4 replies it indicates that there is some sort of network problem and that will be where you need to look rather than on the iPad.
To close the cmd box just type "exit" and push enter.
I can't help you with how to bring up a DOS box in Windows 7 I assume it will be via a similar method.