Here are some applications that will automatically slipstream for you:
nLite:
http://nuhi.msfn.org/download.html
Flexbeta Slipstreamer:
http://slipstreamer.screemer.nu/
Autostreamer from Neowin:
http://www.neowin.net/forum/index.ph...&#entry2453585
Personally I prefer nLite cause it lets you change Windows options before installing it but if you want to leave Windows as is, Autostreamer might be the better choice. You don't really have to reformat but I'm guessing that your download speed problem might be solved if you do.
I always prefer to do a fresh reformat and slipstreamed install whenever a new Service Pack comes out.