trying to recover allocation unit …

I have an old Acer 486 Laptop here and it looks to me like the HDD might be pookered. I have tried to scandisk it and got the message that scandisk could not repair. It has had windows 6.2 on it. I tried to format it and it has been on all night and says trying to recover allocation unit … now at the time I poost this question it is unit number 42, 260. It is an old 400 MB HDD, Seagate model ST9420AG.

How far will it continue to recover allocation units? Is it even worth letting it run like that?