I think it is good to share this stuff with all of you - just in case you need to put any diagram(s) in your entry as an illustration to your presentation/discussion.
STEPS:
1. Draw your diagram(s) in PowerPoint file
2. View the slide
3. Printscreen the slide view (find for PrtSc/PrintScreen on one of your keyboard buttons -> Press the button
4. Open Paint program (if you do not know how to open it - click Start -> All Programs -> Accessories -> Paint
5. Paste the prinstscreen of your slide show in Paint
6. Save it as JPEG (File -> Save As -> name the file (File name) -> Save as type: JPEG -> Save
7. Go to your blog -> New Post (or Edit Post, if you have already posted your entry but you want to add some diagrams -> click Add image icon (third icon from right)
8. A new window (Blogger - Upload image) will appear
9. Click Browse - find the file that you saved from Paint -> click Upload Image
10. Once it's done, the picture will be appeared in your posting box - you can easily drag the picture to the place you want it to be or alternatively you can cut the picture and paste it between paragraphs.
11. If you are satisfied with it, as usual click Publish Post.
Below is the example of a 'diagram' which I created using the steps above:
NB: Apart from using Paint, you can also use another application like Photoshop etc, however I choose to use Paint in this example - considering that some of you might not have Photoshop installed in their PC/notebook.
