Running an FTP for personal use can be kinda scary sometimes.
When I threw an FTP site up (for access to music while at "work"),
I made sure to put in a couple measures:
1) Make sure that none of your other drives or partitions are shared on that PC. Most viruses are designed to replicate themselves by going over shared drives. This protects the rest of your PC for a greater amount of time if you should get infected.
2) Don't use the standard port 21. This come into play especially if it is for personal use. Change the port on your server to use something other than the FTP standard. Then, change the client to use that(those) port(s) when connecting.
3) Scan that drive every day for viruses.
Hope that helps.