XP sp2 professional Blue screen doom Idiot requires help

Hey guy's well i no very little about computers however i decided to finaly upgrade my sp from 98 to XP as 98 is becoming obselete. Anyway i bought XP service Pack 2 cheap off ebay and it all loaded fine and was working well cept i needed to update my sound card driver so i got the download of this website for XP. However halfway through setup it said the software didnt have a valid certificate, well being a fool i ignored this and finished the installation and at the end it told me to restart so duly i did. However following this XP now crashes just before opening the login screen with the following blue screen warning "STOP 0x0000008E (0XC0000005, 0X804EC6E9, OXF4B44560, 0X00000000)". I cannot load it in any mode, safe mode hangs at Driver: MUP. This was the first time i restarted my computer with xp so im unsure wether it was me using the wrong driver or it was a faulty xp. Anyway help would be useful the sound card was a realtek ac-97.