XP Visual styles, can it prevent startup?

I am about to use a different visual style for my xp… i just ran the uxtheme patcher and all, but first I want to know, once I change the theme, do I have to reboot?
And if so, can anything go wrong once it loads back up, as in the system not actually loading up (since the interface is completely changed)
Answer #1
When i 1st installed a theme using uxtheme patcher, it booted up but nothing loaded up on the desktop, i re-started pc and it was fine.