Deleting 1 million blank lines at the bottom of a sheet.

I am using a excel as a data base and scheduling program, lately I have noticed that the sheet has over 1 million lines at the bottom of my page I can't delete.
When I try to use the search bar over to the right of the screen the search bar is really small and as soon as I move it I drag the page down to over 10,000.
My database is only around 300 and the million line thing is new (not sure if my 2 year old had something to do with it).
I think it is slowing down the program and it is making searching difficult, don't want to start a new excel file because I have a number of complex sheets reading from it.
Has anyone got a solution.

Thanks Paul

Tried that but it comes up with a message

"There isn't enough memory to complete this action.
Try using less data or closing other applications.
To increase memory availability consider
-Using a 64 bit version of Microsoft Excel
-Adding memory to your device

Its a new computer and don't have much data on it.

Even deleting 1 row I get a message
"The operation you are about to perform affects a large number of cell and may take some time etc."

Been using this file for years and this is a new thing, something is wrong!

The problem is I have a number of sheets with complex calculations, I don't think copy and paste will transfer the calculations well, can't even drag cell calculations to rebuild quicker. I will have to enter every single cell again, really trying to avoid that.
That is why I have come to this forum.