Freemake and Prism both work pretty well and are free.
You might want to get both because in some cases one might fail and the other would succeed. They probably differ a bit regarding which file formats they accept as input and which formats they convert to.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Ignatz Special; 4 speed manual gearbox; factory air conditioning; one of one
OS
Windows 7 Home Premium SP1, 64-bit
CPU
Intel Skylake i5-6600K, not overclocked
Motherboard
AsRock Z170M Extreme 4, micro ATX
Memory
8 GB HyperX DDR4-2666 (2 x 4 GB)
Graphics Card(s)
none; graphics are integrated on CPU
Sound Card
onboard: Realtek ALC1150; external: USB Behringer UF0-202
Monitor(s) Displays
Dell S2340M 23 inch IPS
Screen Resolution
1600 x 900
Hard Drives
System: Crucial MX100 series SSD, 128 GB;
Data: Samsung Spinpoint 103SJ, 1 TB;
Backup: WD Caviar Green WD30EZRX-00D8PB0, 3 TB
Microsoft Security Essentials and Malwarebytes Premium
Browser
Pale Moon
Other Info
All fans PWM; speeds at idle: CPU circa 500 rpm; intake circa 600 rpm; exhaust circa 600 rpm; CPU temps 27 idle and 47 C load in a warm room (27 C/81 F) when running Intel Extreme Tuning Utility stress test.
I also vote for Freemake. It has never failed me yet and in support hardware acceleration.
My Computer
Computer type
Laptop
Computer Manufacturer/Model Number
Hewlett-Packard/G62-107SA Notebook
OS
Microsoft Windows 7 Home Premium 64-bit Service Pack 1
CPU
Intel(R) Core(TM) i3 CPU M 330 @ 2.13GHz
Motherboard
Hewlett-Packard 1425
Memory
8 GB DDR3
Graphics Card(s)
Intel(R) HD Graphics
Sound Card
Realtek High Definition Audio
Monitor(s) Displays
Builtin
Screen Resolution
1366 x 768 x 32 bits (4294967296 colors) @ 60 Hz
Hard Drives
250 GB SATA Hard Disk Drive 7200 rpm
2TB Seagate GoFlex USB 2 Drive
1TB Iomega Prestige USB 2 Drive
1.5TB Iomega Prestige USB 2 Drive (Samsung)
2TB WD MyBook Live NAS.
I would also vote for Format Factory. You can even crop your videos with it which is very handy at times - e.g when you made shots of animals at a distance
My Computer
Computer Manufacturer/Model Number
HP, Dell, Gateway, Toshiba - 4 laptops and 2 desktops
Microsoft Windows 7 Home Premium 64-bit Service Pack 1
CPU
Intel(R) Core(TM) i3 CPU M 330 @ 2.13GHz
Motherboard
Hewlett-Packard 1425
Memory
8 GB DDR3
Graphics Card(s)
Intel(R) HD Graphics
Sound Card
Realtek High Definition Audio
Monitor(s) Displays
Builtin
Screen Resolution
1366 x 768 x 32 bits (4294967296 colors) @ 60 Hz
Hard Drives
250 GB SATA Hard Disk Drive 7200 rpm
2TB Seagate GoFlex USB 2 Drive
1TB Iomega Prestige USB 2 Drive
1.5TB Iomega Prestige USB 2 Drive (Samsung)
2TB WD MyBook Live NAS.
Keep your eye on this site. Every now & then a company will offer a a paid converter free for a day or 2. Over the past 2 months I've seen 3 or 4 from various companies.
I'm using brorsoft video converter and it seems to be the best one I've tried. It costs me much less time to do the conversion due to its cuda acceleration and the quality of the converted files are fantanstic, just the same as the originals. You can try the demo verison and see whether it can make you satisfied.