You've probably knocked something when you installed the sound card.
Open the computer up, check that the memory is pushed firmly into it's slot(s).
Take a good look around - any cables been knocked partly out? Especially the 12V 4/8 pin plug to motherboard? Does the graphics card need a seperate power cable (assuming you're using a graphics card) make sure it's secure.
Remove the sound card and see if it boots.
Too late now but in the budget sound card range imo you can't beat the Asus Xonar DG, I have two of them.
And just out of interest I'm using an Auzentech X-Fi 7.1 in my main computer, it's a goodie.
At the moment I am running my sound from my Motherboard a ;Asus 970A-DS3P. I am unfortunately not able to use my Auzen Meridian card as support is no longer there as they seem to have gone out of business and unable to get drivers for Windows 8.1 64 bit. The on board sound card is OK but not up to the old Auzen card I was thinking is there a good card out there for a limited budget of say £30 with better sound reproduction for music, not at this so interested in games. Unfortunately my PC is in a small room 5ft 10ins X 7ft 6ins but the speakers are Microlabs 2.1 FC 360 and surprising good. Thanks in advanced for any recommendations. 
Certainly did Mr Mucks and flops did everything you said also disconnected the from the mains, switched off the power supply, removed the battery and switched it off several times and on with the boot switch to discharge any residual electricity in the MB to no avail, still nothing, zilch. After a little time cussing vehemently, swearing and banging head against brick wall decided I had spent enough time on the dam thing, took it all to pieces and rebuilt it still nothing, and went to bed in the small hours and cried like a baby, I think my wife bless her had enough of my frustration and bad temper that day.