An SSD can definitely help. A 120Gb would do nicely. Samsung EVO
Make sure you have at least 8Gb of RAM. Presumably you have removed most startups. Make sure your BIOS settings are proper for fast boot. Make sure to update your chipset and SATA drivers before installing Win 7 Pro on the SSD. Check for a firmware update on the SSD. Use performance tools to evaluate what is stealing performance and monitor effects of any changes made.
My advice get hardware, drivers, BIOS set up before OS. Make one change at a time, keep notes, test with an appropriate app and return to default if no significant change. Most changes will not improve anything. Despite kludging their OS up with built in apps, Microsoft almost always would have already done a performance improvement if it would speed things up. Prepare to spend a day. Make several drive images along the way in case you want to reset and start over from some point.http://www.blackviper.com
- see services and other thingshttp://www.tweakguides.com/TGTC.html
- download the free, you can decide if you want the $5 deluxe version later if you are happy with the guide.
With regard to the network, update router firmware, make sure DHCP and DNS pointers are correct and where you want them and update Ethernet driver and swap cable. Linking should be a few seconds even with a slow system. Also do a power cycle of both the router and the ISP modem/DSL box. If this is a wifi connection the wifi transmitter/receiver may be going bad in either device, but update the wifi driver first.