I installed Ubuntu yesterday beside Windows 7. I chose not to erase the USB because I would lose all my info. Is this safe as of Jan. 14? (viruses etc.) If not, how do I transfer my files from Windows 7 to Ubuntu?
2 Answers
https://help.ubuntu.com/community/MountingWindowsPartitions explains the facts in detail. In your case, almost certainly, Windows 7 partitioned and formatted the hard drive using NTFS, and Ubuntu knows how to read and write files in an NTFS partition, automatically using ntfs-3g, as confirmed here.
Take a look at this tutorial which shows what happens when you open Files and look for the NTFS partition of Windows 7; it will appear in the yellow box of the picture below (although the colors will be different). 
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It is unlikely that security issues in Windows would affect your files so that they cause security issues in Ubuntu, because executable formats are different.
You could transfer files for example with a USB stick. It depends on the file types how you could open them in Ubuntu.
Having both OS'es doesn't slow down your performance.
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