My laptop wont work properly

I turn my laptop, thats running on windows vista home premium, i log in then bam the desktop and the task bar wont show up unless i use task manager to run explorer.exe plz help me!! and if i d try to dpwnload sumthin it just restarts!!
Answer #1
and dont forget itz running on vista
Answer #2
might be just a virus try formating it and doing a clean install
Answer #3
wot should i do? tell meh plz im panicking everyday!!!