I have win 7 home premium on one tower and win 7 pro. on another. My question is can I save a system iso of each one on usb flash drives in case of a crash? My home premium c:/ drive shows 445gb. free from 465gb. so would I have to use at least a 20gb. flash drive. I know New Egg has a large selection of flash drives. Thanks for all help. I have a second hd in my pro system I used to save a complete iso backup on it. 
My Computer
At a glance
windows 7 Professional 64-bitintel i5 4670kG.SKILL 1866mhz. 16GB. (4 x 4GB) 240-Pin DDR3...HIS RADEON 4850 PCIE 2.0 ver.
- Computer type
- PC/Desktop
- Computer Manufacturer/Model Number
- custom build
- OS
- windows 7 Professional 64-bit
- CPU
- intel i5 4670k
- Motherboard
- ASUS Z87-A
- Memory
- G.SKILL 1866mhz. 16GB. (4 x 4GB) 240-Pin DDR3 SDRAM DDR3
- Graphics Card(s)
- HIS RADEON 4850 PCIE 2.0 ver.
- Sound Card
- onboard
- Monitor(s) Displays
- HP w2408h HDMI
- Screen Resolution
- 1024 x 768
- Hard Drives
- SamSung 840 ssd 120 GB
- PSU
- Corsair HX 1050 Gold
- Case
- ALUMINUS FULL ATX
- Cooling
- Cooler Master Hyper 212 EVO
- Keyboard
- Logitech 520
- Mouse
- Logitech 310
- Internet Speed
- 10 mbs
- Antivirus
- Avast full version
- Browser
- Firefox