It's inglorious and often imprecise, but go to MSPaint, select the top-left option in the menu on the left ("free-form select") and draw around the object in question. Warning: you need to do this in one go, but it's not too bad. You can use zoom (view > zoom) if you want a more accurate look. The alternative if this is troublesome is to use the same tool to cut bits off the picture until the only thing left is what you want to cut out - depending on what image you're trying to cut out, this may take more or less time than the other method but it's generally more precise.
If you used the first method then it's already selected so press ctrl + x (edit > cut) to cut the image you've selected out, and then you can paste (edit > paste or ctrl + v) the image down on another in paint. If you used the second method then you still need to select the image, so can use either of the two select modes (top two options in the left-hand menu) to draw a box of some shape around your chosen image (doesn't have to fit the image now, just make sure it covers it all and again, paste it. But remember before doing this to select the bottom-most option in that left-hand menu (it will only appear if you have a select tool in use) - this will make sure that when you paste your selected image down it doesn't have a white border around it, which will cover the picture you are pasting onto and spoil the effect. Thankfully, as long as you haven't clicked the selection box away, you can do this after pasting the image, too.
As I say, it's inglorious, but that's the MS Paint method.