If you're getting Windows update notifications, it's not spam. You should *really really* install them. Your computer is a lot more vulnerable if you don't - you could end up running spyware that allows someone in another country to connect to your computer and use it to send spam, or ddos another computer or network. If you ISP catches your computer doing that, they'll suspend your service. So really, it's in your best interests and I highly recommend it.
..and that's is coming from someone who HATES Microsoft as well as Windows
But I recommend it because I've seen the amount of money some companies have to pay in bandwidth because they get flooded from un-patched computers.
As for the type of computer I have, prepackaged stuff like dell/ibm doesn't go over well with me unless we're talking rackmount servers. Otherwise, it's too much money for generic components. I build my own because that way, I get what I want. Yup, I'm a programmer.. so I'm pretty snooty about what I work with.