Slow Network

I am running a Suse’ Linux server and Windows XP Pro clients. We use SAMBA as our file server. My network is running incredibly slow since switching to this setup. Saving work now takes between 5-10 minutes whereas before it used to take a maximum of 1-2 minutes for large files. My former setup was a Mac server 8.6 and old Mac computers. . . this doesn’t make sense. I am running much faster units now, but it takes three times as long to get anything accomplished.