To do it, open notepad and type the following:

[General]
Manufacturer=Your Name Here
[Support Information]
Line1=Your Name Here
Line2=Your Address Here
Line3=Your Email Address Here

I firmly recommend you to go for block letters as it will bring out a good look..

Now save this in the name OEMINFO.INI in your windows/system32 folder in c: drive (assuming c as your root directory, if it is not your root directory please change the letter).

Now create a .bmp image with 180*120px. Probably get your picture to claim as your O.S.

If your picture is in .jpg or any other format do convert it to .bmp (bitmap picture) format. To convert, you can go for format factory or any other photo format conversion tool.

Now save the picture as oemlogo.bmp in the same directory (C:\WINDOWS\system32 folder.)

After this go to properties in my computer and you will be amazed to see your photo instead of Microsoft...

It only works on windows xp and lesser versions of windows..