SQL: Repair With Keycache
Your myisam_max_sort_file_size is probably too small.

Perhaps your tmpdir hasn't got the elbow room.

First, kill the repair right now.

Add these two lines to my.cnf

[mysqld]
myisam_max_sort_file_size = 80G
tmpdir=/var/lib/mysql (or some other path or mount point)


Restart mysql and do the REPAIR TABLE again.

Give it a Try !!!