Wifi disconnects after sleep

My friend's Win 7 laptop seems to drop the wifi connection when it goes to sleep, although she also says it sometimes drops it even if it has not slept. She is able to fix the issue by disconnecting from the wifi network, and reconnecting.

She bought an external USB wifi adapter, disabled the old one, but it did not fix the problem.

I went into Device Manager and the wifi adapter was not set to sleep to conserve power.

I also went into Power Options and set it to High Performance (still sleeping after an hour) and it is still the same.

She thinks, but is not sure, that the issue may have started when she got a new router/modem from Comcast. But other Win 7 computers in the house have no problem.

Any ideas?

Thanks

If she has to disconnect and reconnect are you sure that she's disconnected?Is it signal icon with yellow triangle with exclamation mark?Limited access?

Also,
Try updating/downgrading driver.
Maybe in driver adapter settings it's set to sleep and it overrides Windows settings.

My friend has been out of town, so I've not been able to do anything more.

Thanks for the info, I will check the driver.