You can use sp_attach_db/sp_attach_single_file_db to attach the sql7 datafile.
After execute this ,the sql7 database will be upgraded to sql 2000 and creat a new database in sql 2000
Say your datafile and logfile of that database is located in
d:\test_data.mdf and d:\test_log.ldf.The query shoudl be
sp_attach_db 'dbname',
'd:\test_data.mdf',
'd:\test_log.ldf'
execute this in Sql2000 Query analizer.Natually it will create a database called 'dbname' with data file and log file.