Vista – virus – can’t install anything

Hi,

1st, I?m not great with computers, so please go easy on me… but

I use Vista and I have a ‘virus’ that is allowing popup ads and not allowing me to install anything.

It does not recognize .exe files

I can download files as the application and a part file, however as soon as the d/l has finished only the part file remains (with no information)

What can I do?

Cheers