I was also going to suggest an online converter (with .doc as the output format)
http://www.zamzar.com/
However Microsoft Publisher uses its own conventions for defining the positions of text boxes, images, etc, so I wouldn't hold out too much hope of the resultant file being very close to the original one.
If you've got an old version Publisher it will probably install properly onto a Windows 7 machine but you'll then need to use the 'Troubleshooter' to get it to run without errors. (I've got Publisher 2002 on this Windows 7 PC, which installed normally and runs fine in Compatibility Mode).
If it's just a one-off need though, the simplest solution might be to download a free (60 day) trial of Office Professional Plus 2013:
http://www.microsoft.com/en-us/evalcenter/evaluate-office-professional-plus-2013
During the trial period you'll be able to create and edit Publisher files. Thereafter you'll still be after to view them.
Once you've solved your immediate problem, if you still need a free DTP solution, look no further than Serif PagePlus SE:
http://www.serif.com/desktop-publishing-software/?mc=FSSPAGEPLUS