I rather doubt this Title is anywhere close to being correct, when you say "Most peoples pcs infected" that has to mean greater than 50% of the whole worlds PCs.
It is almost impossible to get accurate stats on the number of peoples pcs that are infected in the first place. There are many such reports, but they are generally all looking at of pcs that were scanned by such and such, X % were infected, some of those state 80% one even reports 98%. But that is only of a sample visiting a particular site, etc. and they probably went there because they had a suspicion they were infected, not many people visit these sites for a scan if they think they are clean, so any stats would be skewed.
So it is very hard to quantify just hoe many pcs are infected.
One close to your Most statement, is 48% and that is nowhere near correct as the sample size is only 22,754,847, when you consider avast has well over 100 million users and I think represents about 20% of the AV market share, then you get an idea on the numbers.
The recently released APWG Phishing Activity Trends Report for Q3 of 2009, details record highs in multiple phishing vectors, but also offers an interesting observation on desktop crimeware infections.
According to the report, the overall number of infected computers (page 10) used in the sample decreased compared to previous quarters, however, 48.35% of the 22,754,847 scanned computers remain infected with malware.
So you have to be a) careful where you get your stats and b) realise that they may be very skewed.