Extremely slow LAN connection between 2 W7 PCs

I have 2 computers connected through a Linksys SE2500 (http://www.linksys.com/en-apac/products/switches/SE2500/). (http://www.linksys.com/en-apac/products/switches/SE2500/) It's either CAT 5e or 6. There is 20 feet of cable total, maybe. The 2500 is connected to another router. The PCs are W7 home and W7 pro. Working off the home PC to the pro PC is amazingly slow. We're talking 50kb/s. ...