Vista is not the best system.
Your video card is under-powered.
Your processor could be improved upon.
Hi-def, even 720, will make your computer struggle mightily.
You may need to enable shadow(proxy) files within PD.
1. Defrag, delete temp files.
2. Get a much better video card.
3. W7 64-bit will allow for more RAM usage.
4. 7,200 rpm drives, not SSD's.
Sorry 'bout that.
HP Envy Phoenix/4thGen i7-4770(4@3.4GHz~turbo>3.9)
Nvidia GTX 960(4GB)/16GB DDR3/
Canon Vixia HV30/HF-M40/HF-M41/HF-G20/Olympus E-PL5.
Tape capture using 6 VCR, TBC-1000, Elite BVP4+, Sony D8 camcorder with TBC.
https://www.facebook.com/BarryAFTT