By default SharePoint allows a maximum file size of 50MB that can be uploaded into any document library.  Depending on your situation, this might be too much or too little for your needs when uploading. To change the maximum file size, do the following:

 Go to SharePoint Central Administration >> Application Management tab.

Under the Office SharePoint Server Shared Services section, select Create or configure this farm’s shared services.
 

Select your web application that you would like to change.
 

On the next page, go to the Maximum Upload Size section and enter your desired max upload size

The maximum upload size that MOSS will allow is 2047 MB. 

If you increase the file size limit, your site might occasionally time out for users while they are uploading files. To accommodate this increase the default time out property for IIS.   Now you have successfully restricted or increased the size of uploads for your MOSS site.  You can repeat this process if you have multiple web applications for your site collections.