YES!!! anything that has to do with your bootcamp side of your mac will not affect your mac side at all, unless you were to use a full windows installation disc and choose format and then would happen to choose the wrong partition instead of the one labveled bootcamp. Then of course you would wipe all the data on your mac side. But since you say you already have windows insatlled on your mac,and obviously at least lion on your mac side,then you have like a 1% chance of losing any data on your mac side,especially from simply upgrading your windows side software.I have 2 imacs both with mountain lion insatlled and windows 7 64 bit running with bootcamp 4.0 drivers installed. I have been through it all when it comes to installing,resotring windows all versions on my imacs and have learned quite a bit about computers throughout my lifetime. I actually repair them for all my employess and friwends free of charge. I would highly recommend if you havent dne it already is to A,make a fresh time machine backup of your mac side just in case you would ever need to restore it, and B. Use winclone software to make routine backups of your windows partitions in case you will ever need to restore your windows side. Also use the built in system restore feature in windows 7,since its much quicker to do a system restore on the windows side vs a winclone restore on the mac side,however both work well and will eliminate your worries about overwriteing or losing any data on either partition you have installed. Winclone costs only $19.99 and works perfectly everytime.
https://www.twocanoes.com/winclone/