Media Center Suddenly Has No Signal?

all started last tuesday when i swapped an ati radeon 4350 graphics card for nvidia Geforce 210 GPU,,i fully uninstalled all ATI drivers,switched off,,installed nvidia card,,restarted and installed new drivers,things looked fine until i opened WMC,,it was in 4:3 resolution and not 16:9 (the shape of the player,not the program output resolution) and it would not change shape,even though i had been through the setup and changed to 16:9,so i ignored this problem and went on to the tv channel setup in WMC,,it wouldn't find my tuner though (REALTEK 2832U,,usb freeview tuner).After many failed attempts to find the tuner,i gave up,uninstalled nvidia and reinstalled ATI,again,no problems with swapping cards over,but WMC will not work.

Heres what ive tried upto now to get WMC working again:many times trying the standard retuning in WMC,checked outside aerial on a freeview box,works fine,so the aerial is fine,from my outside aerial,i have 4 coaxial extension cables pushed together to reach from front room aerial point to back room where comp is,checked each cable by only using 3 cables,making sure that i have swapped eachcable,meaning i have run a signal using different combinations of cables,so i know that an individual cable isnt at fault,installed blazedtv program from the disk that came with the tuner,which finds upto 75 channels,but all pictures are badly broken up (mainly green and red blocks),with virtually no audio,,,i can hear something,but cant make any sounds out,also,no tv information (tv name etc) is available,just numbers that mean nothing to me,hilst writing this,a search on WMC has returned 14 channels,none of which are playable,only black screen if i press play,time bar is visible,but nothing happens,as this only happened during a hardware change,im fully confident that my signal is perfect,had great picture for 2 years with this setup and although i have had problems with WMC before,any problems have always been resolveable,h yes,,i've also reinstalled windows 7 as a last resort,but with no effect.

i've tried give as much info as possible,but feel free to ask for any more info,,im reasonably computer literate so am open to trying anything,,,thx for reading.p.s,,,i also have 2,,10 metre lengths of coax extension cable,but have never got them to work,which is why i use the 4 extension cable setupp.p.s,,,checked in device manager and the realtek tuner is showing under 'sound,video and game controllersand drivers are up to date.