there could be plenty of reasons out there for a slower startup. Most of the time, in my experience, it's software. Every program you add to a computer has an effect on it... and many programs are setup to load(at least partially) at startup. The more things you add over time, the greater the chance of things slowing down.
First thing you should do is figure out what is actually loading at startup. You can run msconfig and look at the startup tab and see what's running at startup. CCleaner has a tool where you can see, enable/disable and remove startup entries, as do other programs out there.
That's where I'd start... with startup.
Just googled Soluto, looks like it should have a list of your startup entries there as well. Be careful what you go unchecking, but take a look and just see what is loading.