there are some good non virus infected rom sites out there but they are hard to find under the pile of poo that wil invariabley pop up if you search on google. i know a couple that i use but we are not allowed to post rom links. (besides the esa would probably click on em) however if you want a good c64 emulator i recomend
v.i.c.e however if you are a fan of the far supirior speccy then it has to be valadimir kladovs
emu z or if you have money in your pocket
spectaculator you do get 30 days for free though. on the amiga side theres a whole load of versions of win uae
here i found this one tricky to set up though, and as i only wanted to play moonstone i couldent be bothered with it. good luck on reliving the classics man.