Cannot (re) size Excel Window

[Terry]

Help!

For some obscure (to me) reason I cannot re-size Excel. I can 'Size'
individual Windows within Excel but not Excel itself. 'Size' is greyed out
in the top left menu button. Every other program seems OK. I have tried
repairing to no avail. Is there some obscure setting I've missed? I use
Excel 'sized' (as opposed to full screen) a lot and its a pain not being
able to size it. This applies to all workbooks - new and 'old'.

Any help much appreciated

Thanks

Terry