Bro Tom, to capture a picture of your desktop, look at the top of your key board and look for the key that says print screen. On my keyboard, its next to the F12 key...When you find the print screen key just press it. You won't hear anything or see anything but don't worry.
Next stage is to open the paint program that comes with windows. Once paint is open, click Edit and then click paste. The shot that you have taken of your desktop or browser, will then appear.
Then click File at top of page and then click save as. This bit is important. Change the file type from 24 bit Bitmap to JPeg and then save the file to where ever you want to save it on your computer...And thats it

The program i used to actually post my screenshot on the forum is a web site called Image Shack and can be found here
http://imageshack.us/Once web page is open, hit browse and then go to the folder where you placed your picture or screenshot. Double click the file and it will then be entered on the imageshack software....Check the box that says resize image and on the drop down menu, chose the size you want. I always go for 1024x768. Then click the Host it Tab.
Depending on the size of the photo and speed of your connection, the photo will be hosted. You will get 3 lines of text. Just copy and paste the 2nd line of text into any forum such as CU and the small picture should then appear in your post. All someone has to then do is just click on your small image and it will then open up to full size. This way of doing it, is excellent for people who may be on dial up, as it takes so much less time to open up the page.
Hope this all makes sense but please ask, if any of it isn't clear and i will try again.