"Extra" Rows and Columns

Greetings,
A bunch of us are re-introducing ourselves to Excel 2000
at work and so far doing alright. We have noticed,
however, that while we're editing worksheets we'll
suddenly find that our LARGE/LONG scroll bar (sometimes
vertical, sometimes horizontal, sometimes both) has shrunk
to miniature size and suddenly our worksheet has a
gozillion rows and columns.

We're not concerned about printing, as we all know how to
use View\Page Break Preview, but it's awfully annoying to
try to navigate with a miniature scroll-bar and only a
viewable 1.5 pages of worksheet. We should have a
scrollbar that covers about 75% and go from there, but for
some reason it covers about 5%.

Sooo.. any ideas how to either prevent that (preferable)
or at least get RID of them?

Highligting a row, then hitting Ctrl + End just highlights
a single cell way down and over.. so we can't just do
that and delete the extra rows and columns.

Any help is appreciated!
Shane