I have a Spreadsheet that "crashes" on opening, I am trying to understand
why and if I can avoid creating similar problems in the futute.

It is has quite a few Sumproduct, Sumif & Vlookup formulas. But does not
refer to other files, all data is in this file. file is ~20 MB

When I turn to manual calsc and do not "calc" on save I am able to call the
file up.
I think the problem may be formula related. Also If I "range Value: the
file there is no issue on opening.

Are there any guideline or utilities to tell you when you are reaching
"boundaries in Excel

I am on XP, Excel 2002 SP-2.

Any thoughts would be appeciated. ..Thanks