The only problem with windows is that if it's a small little picture and you try to blow it up, your resolution will be all fucked up.
In this case, you can use MS Powerpoint. Paste the image on a slide, then drag it out to the biggest you can get without losing too much detail, then take a screen capture (CTRL+PrtSrn) which will take a photo of everything on your entire screen.
Open paint and paste it in there (CTRL+V) and then just crop out the image you want from the rest of the crap that was on your screen.
Sorry if these seem like retarded ways to do it, but once you get used to doing this shit, it works and it's pretty fast. I spent my entire life without photoshop up until recently so....
and beside, no one else was contributing anything to the thread! lol