First, you should convert UTM to Latitude/Longitude. It is not a simple function, as UTM take on count a number of variables, including the most precise as possible exact Earth geometry (the planet isn't a sphere...). There are several Dati for these variables.

For example, the general acceptance of planet's equatorial radius E = 6,378,137 m, polar P = 6,356,752.3142 and Flattening F=(E-P)/E =1/298.257223563.

Actually there are several Dati for each Earth region, useful when we need very precise conversion. I have a personal experience of a wrong Datum causing more than 100m errors. Depending on the application, such error can be acceptable or not.

A tutorial and conversion UTM --> Lat/Long are very well described by Prof. Steven Dutch, of University of Wisconsin, at
http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.htm
including a spreadsheet to do the conversion.

As soon you have Latitude and Longitude, the next step is to convert them to a cartographic projection. There are several ones to chose from, but most common is Mercator.

If the images you gain from Google Earth are very small related to planet size (say, a city, a street, a farm, a lake) then you can use them directly, as cartographic images (the distortion or error are smaller than a single pixel!).

At this point a question, why OpenGL?
If you are merging such images with a game or other OpenGL program, it makes sense thinking in a OpenGL window. If not, the images can be shown in a single Windows Form, by calling GDI or C++/CLR functions.

Anyway, it is important to store not only the images, but their UTM extents (or already converted Lat/Long) as well.

When rendered in a window, you can use a scale to show Lat/Long, which can be easely converted to X,Y coordinates.
In the simple sample code below, FX is a scale factor. If you make a 360 x 180 pixels window to show the entire planet, then FX is set to 1.
If the same window shows an image 30 degrees wide, for example x1= 106° and x2 = 136° then FX = 360/(136-106) = 12.

Jose Open in New Window

jsbsudha:
UTM includes world very precise format, which isn't an exact sphere. Actually the Earth shape is calle geoyd, simplified to ellipsoids for each region. To render in a precise grid, as the pixels grid, the intermediate conversion to Lat/Long corrects the imprecisions in the plane projections. Then to convert to x,y is as simple as the sample code.

If such imprecision isn't relevant to your purposes, if you don't need neither to know the scale, nor the position nor correct distances, then you can work with UTM directly.

In this case you will simply watch images, which will be at unknown scale.
Also, if you don't need maintain the aspect ratio (proportion) then you can simply map the image as suggested by Infinity08, which is, by far, the simplest approach to the question.

Jose