Time machine restore problems on shared MacBook

My old Mac Mini 2007 has recently failed .

I have a Time Machine backup on an external Iomega hard drive

Before I buy another Mac I just wanted to be sure I have all my data and so I borrowed a MacBook from work which has different user logons.

I created a new user account and logged in.

I opened migration assistant and tried to restore from back up.

my mini had failed on 12 June and all the previous backups can be seen on Time Machine up to that date but these are pink and I am unable to restore from these

The user account login I created is different to my old user account login details - maybe that is the problem?

ideas anybody.?