i am having a problem with booting my PC...After plugging my wireless network adapter in a usb port(does not matter which), it takes 30 secs to pass the bios check and start windows loading. If I unplugged the adapter, it passes bios check in 2 secs... My mobo is a gigabyte z77-D3H.
It could of course be a problem with the bios routines for USB or network adapter discovery; which would make the self-test take a long time, but I doubt that.
Likely what you are seeing is the BIOS attempting a PXE boot, which requires it to try to obtain a network address by DHCP. This fails for some reason, likely because it can't connect to your wireless network without knowing its SSID (and encryption key).
To avoid the problem, change the boot order (in the BIOS settings) to try the hard disk before the network.
The PXE boot should happen after the self-checks and have some information on what's going on printed to the screen (just like the self-checks), try reading the text that shows up to make sure this is the problem. If you can't see any text at all or it does not change, you may want to disable silent boot, quiet boot, splash image or similar in the BIOS settings.