TURNED ON MY COMPUTER AND FONT SIZE SETTINGS CHANGED TO TINY/EXCELL CHANGED TOO
 

I have a several month old Dell Optiplex G520 with Windows XP, Grisoft
professional (AVG) anti-virus, and Microsoft Small Business Edition.
Today I turned on my computer and my settings were changed: for
example: I had set all my font sizes in my outlook folders and
subfolders to larger fonts (the detaul is tahoma 8 and that is too
small). My icons on my home page were I think set to be larger. I had
a good size for viewing webpages. Today, when I turned on everything
was small, and I had to go in and manually change settings again. In
addition, when you type in the email address in the "sender" line, that
now is a tiny font. I had normal size fonts before this change -
however, this is Hard Coded and can't be changed to a larger font.

2) In addition, in my excel sheet that went back to an original
setting, where you have to make it say 2.5 or else it rounds up a
decimal point.

Something is very strange here.

I am also using an old monitor as the tiny tiny fonts in the sender
lines were a problem with the high resolution new monitor I bought, so
I switched back to this old monitor. The tiny fonts in the sender line
were not a problem, until today.,

What could account for this?

I am not a techie at all, so would appreciate very simple language.
Thanks.