Using my iMac in a country with a different power supply standard

Solution 1:

Building on @penguinrob's answer, the specs for the 2007 iMac can be found on the Apple Support KB:

Electrical and environmental requirements

Meets ENERGY STAR requirements

• Line voltage: 100-240V
• AC Frequency: 50Hz to 60Hz, single phase
• Maximum continuous power: 200W (20-inch models); 280W (24-inch model)
• Operating temperature: 50° to 95° F (10° to 35° C)
• Storage temperature: -40° to 185° F (-40° to 85° C)
• Relative humidity: 5% to 95% noncondensing
• Maximum altitude: 10,000 feet

It looks like you should be able to get by with the IEC cable/adapter; the transformer can handle 100-240V, so you likely do not need an additional transformer.

Solution 2:

According to http://www.apple.com/imac/specs.html (under Electrical and Operating Requirements), it specifies a line voltage of 100-240V AC, so if the country you're going to provides plugs with output in that voltage range, you should be fine.

According to http://web.archive.org/web/20071025020751/http://www.apple.com/imac/specs.html (snapshot of the imac tech specs page from October 2007, the same voltage requirements apply.