Interesting experience over the weekend. I consider my XP home PC to be pretty well up to date and decided to load the Beta copy of IE 7 - it looks very good.
All went well until this morning when I tried to access a secure web site receiving a message that it did not recognise the browser. Gave the options of loading IE 6 - which took me to the IE 7 Beta link again or Netscape. Eventually ran Netscape and very impressed with the features on offer. Ran the built in scan and it discovered a "unknown" trojan and an item of spyware. Rather a surprise that as Norton is bang up to date and regularly run and also Windows Defender likewise.