Wireless problem between router and laptop, disconnects a lot

Up until recently I had wimax connection and d link wireless access point and it worked fine. But now I got ADSL and some Pirelli router. On my PC and PC in next room where laptop is it works fine, speed and all and there's no disconnect like on laptop.
It works for a while but then it suddenly starts disconnecting every few minutes for a while. Then it stops and works for a while and then it happens again.
I installed newest drivers for wlan card on laptop but didn't help.

Anyone got idea what might be the problem? Laptop is Dell Studio XPS 1640, wireless card is Intel Wifi 5100 agn.
Connection returns after few seconds but it stills screws everything up. Router and laptop are on same channel so thats not the problem.
Also it drops whole connection not just internet, because I see little sun on wireless icon and it reconnecting.
Windows 7 64 bit.

 

Install this application (it's free) and scan wireless channels. It's possible that there are other wireless networks on the same or neighboring channels that affect your connection quality. It can also be affected by cordless phones and/or Bluetooth devices that work on 2.4GHz band.
After you've scanned wireless channels change yours accordingly- so that there's no one on the same channel or any channels near you if possible.
Another possibility is aggressive power management of Win 7- go to power management settings and disable power management for wireless card.

 

I just tried installing intel's wifi program but it says adapter not found...

Running that program as we speak. On my main PC I'm only getting 1 connection near, while on laptop one more. They both are on channel 6 while we're on 1. I know 6 is default for that router(all using it) so I switched as far as I could. Getting 3-4 bars toward one connection and 2 toward other.

As for the other devices, there aren't any that could cause this. There's PC in that room but this happens with it on or off.
Turned power settings to max for wireless, there wasn't disable option, we'll see how it goes.
I don't know why intel program doesn't work though.

Edit: Also I just caught 2 more connections pretty far and barely for some time, one was on channel 11 and one was on 1, but they disappeared quickly, plus laptop is used around house so it's not getting all of them every time. Atm it's 5 inches from router.