I've just installed Maxthon2 Browser onto my External Hard Drive. I've been told by a bloke in our local computer shop that if you install software onto an external hard drive it will run slower ... Is this true?

Hehe...nope.

Data transfer is generally slower for external drives but I doubt whether you would notice it in an application

ok, thanks for your advice. I think you're right because i uninstalled it from external drive and installed on built in drive and didn't really notice any difference