Here is how I convert an excel (MS Office 2007) graph to EPS so that I can use that graph in a TEX file.
1. Open MS Excel. Copy the graph to a new sheet and be careful so that it fits in one page (you can double check if the graph fits in a page from print preview option).
2. Go to File-> Print-> Properties-> Advanced-> Postscript Option and select EPS.
3. The file will be saved as EPS so give the file an extension .eps
4. Open the GSview and open the .eps file you just saved. Go to File and select ps to eps. The file should be given an extension of .eps. This is the final eps file that you can insert in your TEX code.