1) Firstly for .rar files
.rar files are compressed files like .zip files. But that is done through a software called WINRAR.
You can download WINRAR Soft free of cost from their official website and/or download.com
( If you are wondering why would anyone use WINRAR over Winzip, the fact is Winrar is better and more secure)
2) Office 2007
Microsoft's earlier version of office i.e. 2003/XP used to have files as .doc .xls and .ppt
But newest version of Office 2007 offers .docx .xlsx and .pptx
If you come accross any of these new files, this means that they are new Office 2007 files.
The problem is that these files are not backward compatible ... meaning, you cant open them in Office 2003
So, microsoft has released a patch which will make you Office 2003/XP compatible with Office 2007 files.
You'll have to search it over ...
i hope i have clearified ur doubts