Strange DL Speed issue

[Guest Rahul]

I know a speed issue can be due to a 1000 reasons.. my speed stays at few kbs (~5) i used to get great speeds.. just one day i lost it

But I have these facts to narrow down the issue

-i use a 100mbps fibre conn

-other computers with's our home network gets good speeds only my computer has the issue

-the issue exists with all bt clients

-firewall is off and no antivirus for the time being

-I EVEN TRIED REINSTALLING WINDOWS!! still problem persists (both xp and win7 has the issue)

-my browsing and http downloads are really fast

-upnp seems to be working as i can see my bt ports listed in the router

now the only thing that i can think of to change is my wireless adapter. Do any of you think thats possible cause?

I would be so thankful if anyone could suggest me some probable causes/fix for this

Thanks a lot for your time Guys