thats kinda what happens when you transfer from a direct connection to a wireless connection. if it doesnt have a secutity key, someone could be on it and downloading something, any speed drops a little bit when your downloading. If the router is in the next room or next floor, the speed is gonna drop.... but it might be because it is out dated, idk

FLiPzIdEx wrote Type of router: Netgear Wireless Super G
Firmware: Has latest available on site

So it was fast for like five years, until last month it slowed down not only for my laptop also my xbox. Its fast when connected with Ethernet cord. I tried changing the channels but no luck, any ideas?

The easiest way to increase speed when using wireless is to use Wireless MAC Filtering, and by setting a password on your router. When you dont have a password anyone can join your network (like free wifi at starbucks), but if you put a password on it they will need to know the password in order to connect, and for even greater security Wireless MAC Filtering offers you to be able to only allow the mentioned PC's, consoles, and wireless devices that you select to connect. So even if someone has your network password they wont be able to bypass WMF. Also like the other guy said, walls, other electronic devices, and sometimes even the weather can effect wireless packets from reaching there destination. One last option you can try is to reset you modem, then your router, then do the following steps i mentioned above. It will give you a clean slate, and you will now that nobody is connected. Also if you would like to check if anyone is on your router, download the free version of "Netmagic". It allows you to see all connection incoming and outgoing on your router. Hope i helped.