For simple resizing you don't need anything else than Microsoft's on-board graphic program MSPaint (users of other OS' have to find it themselves ).
I made the whole tutorial on a German version of WindowsXP, so there might be some confusing words, but I think it shouldn't be a problem for you to figur what the entries are called in English or whatever your Windows language is.
As example I use JoeMI6's Exo-Force MOC.
Go to your Start menu and try to find the entry pictured below (probably Start / Programs / Accessories / Paint)
Now go to File / Open... and open the image you want to change.
After opening it you might want to check what the dimensions of your image are. This can be done via Image / Attributes.
You will see window similar to this one:
You can see now the dimensions of your image, width x height.
The shrinking itself will be done with another function of the program, but this screen is important since you have to know what the original size of your picture is.
Close this window without of changing anything and go to Image / Stretch/Skew....
This screen will open:
Now you have to enter the percentage you want the image to be shrunken.
If the picture is originally 2400 x 1800 and you want it to be 800 x 600 you have to enter 33% for both values at the upper "Stretching" fields.
After clicking on "OK" you will see the result.
Check the dimensions again at the Image / Attributes window. They should be smaller now and the result should be something like this:
Now you can save the image, you might save the changes in a new file if you want to keep the original High-Resolution image (That is at least what I do)
Now a final word about dimensions:
As a long time user of a 1024 x 768 resolution for me pictures that are not larger than 800 x 600 pixels (or 600 x 800). In some cases images of a size of 1024 x 768 pixels are okay, but this is only the case for large models with lots of details. For small creations sometimes even 640 x 480 works perfectly!
Hope all of this is understandable, please let me know if there are any problems with this tutorial so I can edit it to make it easier to understand! :smile: