You can put your images on external drive and if you do not want to plug the external drive all the time, I would suggest you to build smart previews in Lightroom which would not even take much room on your system.
How to create Smart Preview : Adobe Photoshop Lightroom Help | Smart Previews
Thank you Jitendra, i know i can but is it a big step down performancewise to work from external drive?
I keep all my photos on an EHD; it works fine for me. For your system, you can easily run your own experiment by putting a file on the EHD with a copy on the computer HD. First edit the EHD copy and the perform the same edit on the computer HD. Time each edit and report back on your findings.
Thank you Jitendra, i know i can but is it a big step down performance wise to work from external drive?
As long as the LR Catalog, Previews folder and Camera Raw Cache remain located on your faster C: drive you shouldn't see a loss in Develop module performance. For the Library module you will need to build Standard Previews on import and keep them updated when editing images. After editing a group of images in the Develop module select all of them and go to menu Library> Previews> Build Standard-Sized Previews. If you have a need to review a group of images at 1:1 view select them and choose Build 1:1 Previews. Also keep in mind the Library module should be used for reviewing and rating groups of images since it uses the already rendered previews. The Develop module renders images real-time. which is significantly slower. Following these workflow procedures you shouldn't have any performance issues with images on an external drive.
thank you for your expertice. have a great day