If you facing problem of css and design after installation in windowWindows please follow the following stepsteps:
step 1. php bin/magento setup:static-content:deployphp bin/magento setup:static-content:deploy
step 2. php bin/magento indexer:reindexphp bin/magento indexer:reindex
step 3. make sure apache "rewrite_module" is enableenabled and then restart the server
step 4. delete cache folder under var/cachevar/cache
The above stepsteps are working for me.I hope this will work for you also.
Let me know if you still facing any problem.