[louie]

usually after i turn on 1 houe, the imac is very hot.
you can tell by putting your hands on the outside of shell.
is there any way to make it cooler?

[gooser]

louie, is this your g3 imac? if so they do run warm. ignore it. just the way they were designed.

[drmbb]

Going by touch is usually pretty meaningless. Many machines (not just Apple's) run at what feels like a very warm temperature. But, they are in fact operating well within their thermal design limits.
My powerbook runs far too warm to keep comfortable in my lap for an hour, but the temperature readings from the internal sensors will show that it is in no way overheating.
As long as it is operating normally, I would not worry. And, all Apple machines for years now have been built with thermal overload protection built in - they will abruptly power off if any critical sensor detects a temperature above the design limits.