Unfortunately this ongoing issue is outside my area of expertise if you will as primarily I only provide Anti-Malware support and from experience I do not think your machines problems are actually malware related as in the cause...
With this in mind I suggest you seek further assistance with the excellent Tech Staff we have here in Geeks to Go. So please create a new topic in this part of the forum:-
Windows Vista™ and Windows 7™
Explain the problem/situation and by all means mention I advised you seek further specific support with this matter and include the below URL if you so wish:-
http://www.geekstogo.com/forum/topic/303213-computer-will-not-boot-stuck-on-black-screen-after-dell-logo-appears/page__pid__2029305#entry2029305