Unfortunately Excel versions 2003 and earlier have a maximum limit of 256 columns (i.e. up to column IV). But in the newer versions the number of columns has been substantially enhanced, You can now have 16384 columns (up to column XFD)
So I suggest that you upgrade to Excel 2007 or 2010.
However as workaround you may able to utilize your rows and use your data vertically by transposing it. If you need help in this regard send me your file and I will try to set it up for you
Hope this helps
Sure, go to www.wikisend.com and upload the file there (no need to sign up). You will then get a page that has the File ID and Download Link. Copy either the File ID or the Download Link and come back here and paste it in your reply.
If the file has sensitive information you can either replace the sensitive data with dummy values, or let me know before you upload it.