Microsoft's encryption in Office docs has gotten a lot better.   We typically use FTK's or Paraben's decryption suite for cracking these passwords.   If it's a long password, the distributed architecture of these tools helps.  They are obviously commercial tools though.   I haven't seen any open source tools for this.

Thanks for the tips - I've used the FTK Imager program but didn't know about their password product.  I just looked through the user guide and didn't see that their tool does Office 2007 docs though.

I'd not heard of Paraben before but just looked at their products.  If I need to go commercial I'll probably lean towards the Elcomsoft tools since they seem to be cheaper, unless someone has a reason to avoid them.  I'm currently trying their Office recovery tool in demo mode, using a series of dictionary files.  Their brute force portion is pretty limited in demo mode, but the dictionary mode is available.

Although it may not be usual to have 20 PCs at home.

it is too hard to crack office 2007!