Try clicking on the AO icon top left. You should have a size menu for the window.
Can you change the size from this menu and fix the problem?
It looks like your fonts are way too big by the way in the announcement part too.
Is this happening since the last patch only?
Did you change anything on your system?
Do you see anything unusual elsewhere with another software or the system itself?
If you launch AO, does it work normally?
If the answer to the last three questions is "no", it looks like some corrupted file(s) that may require a reinstall.
If the answer to the first question is "yes" then it's likely the last patch that screwed it all.
I patched and doesn't have this issue by the way, which means nothing really for your case, except it's not a general issue.
If you reinstall, reminder:
You need to save and then transfer to your new install your preferences and profiles:
Your preferences and profiles that are stored there:
C:\Users\C\AppData\Local\Funcom\Anarchy Online
(Copy the folder and put it at the right place on your other system)
And ALSO any of the following folders IF you need them:
Skins
C:/Users/C/AppData/Local/Funcom/Anarchy Online/
random-ID-numlber-here/Anarchy Online/Gui/
(This location can be chnages in "Settings" in the AO launcher)
Scripts
C:/Users/C/AppData/Local/Funcom/Anarchy Online/
random-ID-numlber-here/Anarchy Online/scripts/
(This location can be chnages in "Settings" in the AO launcher)
Screenshots
C:/Users/C/AppData/Local/Funcom/Anarchy Online/
random-ID-numlber-here/Anarchy Online/Screenshots/
(This location can be chnages in "Settings" in the AO launcher)