I have downloaded unity and when i start it it stays at the splash screen (with the cars and stuff) and never loads. Sometimes it opens up this window that lets me open or create a new project. Whichever i choose it disappears for a bit then a window containing this pops up “Spel\unity\Editor\Data\UnityExtensions\Unity\g…\UnityEngine.UI.dll” and it stays there until i either kill it with task manager (doesnt always work) or reboot my computer. Im using windows 8.1
Did you see the Editor log file?
Which can be useful to know what is happening there.
You can press Alt when unity is starting, to force opening the project wizard and then you can create a new project, did you try this?
Any anti virus running?
Has Unity ever run for you?