BitLocker encrypts the entire hard drive. I run Visual Studio and build projects much of my day. How much will BitLocker slow me down? (dual core laptop with 3GB of RAM).
MaximumPC ran a few tests:
Benchmark: (Unencrypted Drive;Encrypted Drive)
sure, running 3D benchmarks doesn't really make sense as you're hardly going to encrypt a gaming rig, but in the end it's simple trade off: performance for security.