Go to Options > Audio Settings and select ASIO4ALL v2 as your device. Set the buffer length to 512 or 1024 samples to reduce CPU load.
You must have Windows 7 Service Pack 1 (SP1) installed. Processor: 2GHz Intel or AMD CPU with full SSE3 support. Storage: At least 4GB of free disk space.
Many classic "gold standard" VSTs were never updated to 64-bit. Running them in a 32-bit DAW prevents "bridging" issues and crashes.
Remember that FL Studio is not "free" software. You must log in via the "About" panel with your Image-Line account credentials to remove the trial limitations. Conclusion