Wifi connection dropping every 5seconds or so

Hello all,

Recently my Laptop connexion in wifi just got worse and worse in just a few days. I have no idea why.

First off : my router is fine, my others devices have their usual connection and it is stable (even others wifi devices). I've tried pluging an ethernet cable and the issue was here too so I'm pretty sure it comes from my computer.
I've ran Malwarebyte twice now, full scan with AVG and nothing came out. Drivers are up to date but I've tried to go to the constructor site (Atheros) to get some OG drivers but I couldn't find the ones for my Dell Wireless 1515 n adaptater. Driver wise I've tried uninstalling my wireless thingy but to no sucess either.

The problem is really strange, when I got to site to check my internet speed, the connexion appear as it should be then drops to 0 in matters of seconds. Windows does not detect any problem with my connection either at any time.

I've also tried : installing no coin ; repairing firefox ; resetting router (who has a fix canal of transmission and is not on auto) ; turning off mac filter and differents securities on the Wifi (WPA and WPA2) I would have used resore point of windows but for some reason there was non available from before the bug arrived.

Internet explorer won't even load some sites (straight up to "we can't load that page) whereas firefox still tries (and never suceed or barely in some cases)

I'm in a house so security of the router is ok (and I got WPA and mac filter)
I'm under Windows Vista, the laptop is Inspiron 1750.

Anyone having a clue to what is happening here? thank you for your time