Fansubs... no.
But I'll help out. Okay, make your AMV as normal, yadda yadda export yadda yaddda...
Now, get the following things:
CCCP:
http://delta.movax.org/cccp/Combined-Co ... -07-28.exe
AVIsynth:
http://prdownloads.sourceforge.net/avis ... e?download
VirtualDubMod:
http://prdownloads.sourceforge.net/virt ... p?download
Set AVIsynth to assosciate AVS files with notepad when it asks. That should be the only installation question for all that stuff.
Okay, now. Open VirtualDubMod. Go to the open menu, and select "DirectShowSource" from the drop-down list in the bottom-left. Now set filetypes to "All Files" and open your WMV. Voila, a WMV in VirtualDub.
Now go to Filters. If you just wanna crop, Add a filter, then add "null filter" or whatever the null option is. Then click cropping and adjust.
Someone else can help you with anything after that as resolution and stuff is dependant on source and crap... I can't just give you a miracle solution, I can only tell you how to access the tools you'd need to crop.
Best of luck.