Fonts screwey

[VIKTOR2020]

I'm sure there's an obvious solution, but I can't see it.
One day all my fonts changed into a really crummy mess with some letters in bold and others not. The loops on "d" and "p" don't even meet to close the circle. This shows up in Word documents, Internet web sites, and email. The stuff on my desktop seems OK.
I've tried changing fonts in Windows Vista and messing with my graphics card, but nothing gets it back to the readable form it used to have.
Any suggestions gratefully accepted.
Thanks