changed video card now black screen after boot

[fosterd78]

so i got a new psu (rx-530ss atx) 530 watts to power this graphics card a friend gave to me its a saphire hd4850 and so i got it all it and currently i dont have a dvi cord so i hooked it up through s-video for now and was just testing fps and stuff and i went to play a game and it said couldnt load 3d or something so i went to update my drivers for the graphics card and after i did thst it asked me to restart the system so after i did it booted up and showed windows then made the dell start up noise (i have a dell inspiron 545 2.66ghz 8gb ram ) then it just goes black. and if i unplug power to my graphics card i can use vga on my onboard graphics like normal. soo any suggestions??? UPDATE ok so i did what that guy down there said i uninstalled all drivers using this program then did a restart and it installed my card and started fine then it said i needed to restart my comp to complete installation and im back to square one. boots up said loading windows then bam black screen and still makes start up noise . also it says its a ati radeon 4800 series if that helps

 

[d1rtydeedz]

You have to do a clean install of all drivers. Uninstall all drivers from your previous gpu. Then install all drivers for your new gpu. Try it and let us know.

 

[fosterd78]

You have to do a clean install of all drivers. Uninstall all drivers from your previous gpu. Then install all drivers for your new gpu. Try it and let us know.

thank you for replying so fast. im really new to this so could you give me the steps to do that?