Windows 7: Wireless connectivity problem

I have 2.7 dual core, 1 GB ram running windows 7 32-bit.I am using Tenda mini usb adapter W541U V2.0.Whenever i connect to internet it gives good speed but after a while "no internet access appears" or sometimes dont appear and internet speed drops down to almost none.I cantacted Tenda support centre and installed driver they suggested.Now connectivity drops but less frequently.I replug USB adapter and it work well for a while.What should I do??

How many unpowered USB devices do you have?

Are you using homegroup, or workgroup?

Ken

I would plug your Wireless Adapter directly in the back of your tower/Laptop... Don't plug it into any hubs or extentions

i am using WORKGROUP. and using extension cable for USB adapter.No other USB devices attached to my computer.

Some more details

any help

Under the power saving settings...
Make sure its turned off

i have already checked it off

The driver I installed from RaLINK website suggested by Tenda Support centre have two options for installation
Driver only
Driver and wifi utility
They suggested Driver only but it didnot worked well.Now i have reinstalled driver with utility.Now network drops less frequently, although it shows network connected.