Minimum System Requirements Office for Mac 2011 (from the Office for Mac Help.com):
- A Mac computer with an Intel processor
- Mac OS X version 10.5.8 or later (Leopard or higher)
- 1 GB of RAM or more (with Snow Leopard at least 4 GB; with Leopard at least 2GB)
- 2.5GB hard disk space
- 1280 x 800 or higher resolution monitor
- DVD drive or connection to a local area network (if installing over a network)
- Safari 5 or later recommended
- Outlook requires Exchange 2007 or higher
If you barely meet the minimum requirements, you will most likely not be satisfied with the performance.
OS X doesn’t like being run on a hard drive without a certain amount of free space and will generate “insufficient memory” error messages if the OS doesn’t have room to write virtual memory to. If the OS cannot save correctly, you could lose some of your files.