If the IDENTITY column is defined as (0,1), and the table is empty, and there are no foreign keys involved, just issue:
TRUNCATE TABLE dbo.ImportedFiles;
If the table has foreign keys - or in any event, for that matter - you can just override the value:
SET IDENTITY_INSERT dbo.ImportedFiles ON;
INSERT dbo.ImportedFiles(col1, col2) SELECT 0, 'UNKNOWN';
SET IDENTITY_INSERT dbo.ImportedFiles OFF;
I have confirmed that @Avarkx's answer also works - reseed with -1 should yield a next insert of 0. So I'm not sure what version you're using where this doesn't work (I have no idea how to interpret "doesn't like it").