Excel Spreadsheet Size

We have some users having problems with Excel spreedsheets. They seem to get corrupt often. The size of the spreedsheets are arownd 25-30 MB each. I have heard thats to big for Excel and should be done in Access. Are there any maximum file sizes forExcel? If so where can I find info on this?
(the PCs are IBM PL300 PII 400 & 320MB ram