I think you're out of luck. Seiko has really downgraded its legacy product support and it has minimized its application and driver software available for download. You can try using a Windows 7 package. To find software for your SLP 100 you'll have to go to a third party site like Drivers Guide. The link below is for version 7.0.3 while it says its for the SLP 420 it's actually compatible with several models
Seiko SLP 420 Free Driver Download
Important tips when finding and downloading application/ driver software from non-OEM sites
1. Never install any application from a non-OEM site that says it will scan your computer to determine what files you need. - search using the manufacturer name, model number, and current operating system on the computer you want to install the device on.
2. Only install the files you found. Never download any software suggested.
3. When installing the downloaded files, always select Custom Installation to make sure you only install the software you need. In this case only the application and driver files, nothing else ( no driver updating, security scanning, toolbar, etc. programs).
In the specific case of the Seiko Smart Label printer make sure your printer is not hooked up until the Seiko software tells you to.