Difficult to say, since for all we know you have a crapload of software loading at boot. I worked for a University one time, and there was one professor who had like a 3 year old computer. He kept complaining about how slow it was, and then you'd go out and find he insisted on having the full Adobe Creative Suite loaded at all times along with a dozen or so other programs. For all we know, you're the same way.
Also, there was mention of registry cleaners, so who knows what damage those might have done to your OS in the past. And it's a minor thing, but an important distinction none the less. You don't have two processors, you have a single processor with two processing cores. It's not the same thing as dual processors, even though that is how Windows will choose to represent it to you visually.
I have a Dell Inspiron 1545 laptop running Windows 7 64-bit, 2gb ram, and a Intel Core Duo 2.20 GHz processor. It takes an average 5 minutes between pushing the power button and loading the desktop. At this point I think it is either a bad motherboard, bad hard drive, or other defective hardware. I ran both Super Anti-spyware and Malware bytes, they found nothing. I checked for updates and cleaned the registry. I've gone through msconfig and removed unnecessary processes. Using msconfig I double checked that it was using both processors. I also uninstalled any unnecessary programs. Finally I performed both Windows and Dell hardware diagnostics. Everything passed as fully functional. So I'm left with the final question, what would be slowing down the boot so much? One important note is that Dell boots with normal speed. It's when it starts loading windows it slows down so badly. Once it is on it runs very slow. Any ideas on what I'm missing?