If your PC is not detecting your newly installed RAM, don't worry, as this is more common than you might think. Simply open your case, re-seat the DIMMs, and ensure they're in. If that doesn't work, remove all the DIMMs, and insert them one by one until your PC boots normally. Often, you can reinsert all the remaining DIMMs after this without issue. You can also check your RAM health on Windows to eliminate the possibility of bad or defective memory sticks.