Nope. There's no way to reduce the number of rows or columns in a worksheet.
You can hide them like the prodigal son Harald suggested or you could actually
use some code that won't let the user scroll too far right or too far down. But
that requires a macro.
If you want to try that:
Option Explicit
Sub auto_open()
With Worksheets("sheet1")
.ScrollArea = .Range("a1:f22").Address
End With
End Sub
Excel won't remember these settings after you close it and reopen the workbook
(that's why it's in auto_open).
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
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Personally, seeing all those columns doesn't bother me. I don't think it
bothers most excel users either. And if you're new to excel, then give it some
time and it won't bother you either <bg>.