Don't buy another program to upload screenies!!!
Use Irfanview to resize your screenshots to the correct size for the forum or use Photobucket for your screenshots.
Guidance on Image Optimisation: www.mission4today.com/...mp;kid=455
IrfanView is a free image optimization program that is able to read .tga files which are what the screenshots are by default. I believe one of the recent patches will allow you to have them taken as .jpg but you need to edit the conf.ini file.
To upload a picture directly into the post it must be no larger than 100 KB.