@megamanrulesall,
I'm told essexboy (an expert here in avast's forum) was already notified so to check this topic later.
In the meantime, since you have a laptop (and no Windows VISTA CD/DVD/UFD, according to your post), please check that the F8 key is "really" F8. Some systems use an "Fn" special key so to activate the F1...F8...F12 keys. Otherwise, the same F8 key is actually something else.
In addition, instead of just pressing F8, "tap" several times (as oppose to pressing just once and holding the key).
In the past, had you been able to see the Windows boot menu with F8, ever?
BTW, please add in your next post additional information (besides answering to my questions above and trying those suggestions):
Vista Home Premium, but x32/x64? SP1 and SP2 installed? Avast Free or Pro or AIS? Which exact version of avast (6.0.1367)?