Troubleshooting WiFi issues is a nightmare without specifics, and tedious even with specifics.
There are two assumptions I make:
- You have a cheap router
- You have a cheap Wireless NICs.
Don't take it personally, it's just that most free/cheap routers ISP's give people are garbage and most Wireless NICs are cheap and basic.
- Uninstall any crappy apps or non-driver software that came with the Wireless NIC, you want to use Windows drivers and nothing more; Ideally Windows will detect the NIC and install drivers, otherwise you want to manually install the driver from the .inf file.
- Go to the Wireless connection properties, configure the adapter and set preferred mode to 802.11g instead of mixed mode or b/g/n
- Remove any old remembered networks from the "manage wireless networks" link in the Network and Sharing Centre
- Logon to your router and set a WPA2 (AES) instead of a WEP or WPA (TKIP) security key.
- Set the router's wireless mode to 802.11g as per step 2.
- Save changes (router will probably reboot) and reboot your PC for good measure. Probably unnecessary but it depends on your Wireless NIC and whether you had to uninstall non-microsoft WiFi management software.
If it doesn't work now, your Router is probably buggered. If it does work, you can try enabling things like Mixed mode
for better performance and enabling 802.11n if both router and card support it.
99% of all "I'm having wireless issues" I solve are to do with godawful 3rd-party utilities that pretend they can manage WiFi connections but in practice just fail hard and cause people to come running to tech support :\