There is a maximum file size for any given FileMaker 5 file. I seem to recall that it's something like 2 GB, but I may not be remembering that figure correctly.
Newer versions of FileMaker are not limited to 2 GB.
And I forget if this is even possible in such an old version of FileMaker, but you may be able to store the photos "by reference" and thus greatly reduce the size of your files.
That's the concept but you can't just enter a URL like that directly into the field.
If it's possible, it will be a storage option you specify for the field or that is avaialble to select in the dialog used when you insert the picture.
The hard drive or partition containing the database is local or network? Size and Free Space? Operating system on the drive or just data?
Size of the database file?
Size limit for a FileMaker Pro 5, 5.5 and 6 database - 2Gb
FileMaker Pro 7-11 database size limit - 8Tb (terabytes).