Hi Gerro,
There's no simple limit apart from the 2GB maximum size of an .mdb file
or MSDE database. There is also a limit on the record length that the
built-in import routine can handle: IIRC it's about 64k characters.
Likewise, the import routine isn't designed for files with more than 255
fields per record.
I've imported text files with millions of records, and ones more than
100 MB in size. With really big files, it can help if you start by
creating the table manually, with no indexes, and compacting the
database. Then import the data and finally create the indexes and
relationships you need. This seems to make the import go faster and may
reduce the chance of the 2GB limit being breached during the import.