MS-Excel can create some lovely graphs and charts, but when you try to copy and paste them into some other Office application, the proportions and formatting get all screwed up. If you've added text labels or guide lines using the drawing tools, this is even more noticable.
However, I've discovered that IrfanView, the best damned freeware file viewer out there, can handle the Enhanced Windows MetaFile (EMF) format just fine. If I paste a chart from Excel into IrfanView and save it as an EMF, it looks exactly like it did when I formatted it in Excel. When I then copy that EMF file from IrfanView into PowerPoint, it's just the way I want it.
Consider this an official recommendation for IrfanView. I've used it for years. It's a good, old-fashioned program that doesn't demand a registry entry -- you can drop it in any directory, and it will run from a floppy or a USB thumb drive, so it's portable. I have yet to encounter a graphics format that it can't handle, though it requires plug-ins for some of the odder ones (like "MrSID", a format that I've only seen used for geographic data). With the right plug-ins, it even handles audio and video formats, though not as well as specialized media software.
IrfanView will let you crop, resize, change to grayscale, reduce the number of colors in an image (which can really shrink the size of line drawings), tweak contrast, brightness, and gamma. It has a few other useful-but-minor image-manipulation features. I almost never have to fire up a paint or drawing program unless I'm adding text or color to an image. By the time CorelDraw finishes loading, I can have an image loaded, manipulated and saved in IrfanView.
Every time I've introduced a co-worker to it, it's soon become part of the standard installation on the machines in the office.