Cannot set up wireless connection. See bars and computer says conectivity is good, but still cannot connect.

SOURCE: wireless connection?

no,,,,,,,,In wireless connection at first you have to configure in the d-link router for that you have to go
the router page in that one option is there wireless you have to give there ssid,channels,encapsulatrion etc...
you have to configure it.and you have to give protection from the outsider then you configure the wireless
web key tp portect it.
after then you have to installed your usb adpater and installed the driver of the adpater
after then you have to go the destop in there my network place right clik on it>properties>in there
you get the wireless option right clik enbale after then go to the view the wireless network same right clik the wireless icon.
connect it.if your firewall is on then off and any proxy server is there then remove it then you get it......

SOURCE: there is ahen the conection for 3 min the net faild and reconnect

On your desktop tray, you will have a w-fi icon (may be just the usual network icon). Check your signal strength there. If it is low, you could be too far away from the router. Another thing that can cause problems are microwave ovens and cordless phones. The latter often uses the same frequency as the router (2.4ghz). If you have one of these cordless phones near either the router or the PC, the interference could be significant.

Look at those things, and if you can provide a little more information (does it reconnect on it's own?), I can offer further suggestions.

Cheers
Nick

SOURCE: wireless conection on off on off every 3 second

try the following separately each time:
1) Turn off the power off the router, turn off the PC, turn on the router, turn on the pc after a minute or two.
If this does not work, Try:
2) Remove the Wireless router Definition on your PC and reinstall it. Make sure that you are using the correct Passwords between the router and the PC.