1) Deleting Prefetch data may increase boot time slightly, but only the next time you boot Windows. Each subsequent boot should proceed normally, since the prefetch data will already be present for the programs Windows loads when it boots.
2) Take a look at the startup tab items in Msconfig. Uncheck anything non-essential. You can research on this or ask here. I generally keep only the AV, touchpad and my password manager checked. Sticky notes also if you use them.
3) You can use Soluto to tell you what programs are consuming boot time.
Soluto