What version of mcafee have u? 9.15 or better is win 7 compatible . Win 7 wipes the xp disk doesn't it? So you had to reinstall mcafee was this the case?
What message is the security centre throwing up? Does fix actually fix it?
Had you registered the version of McAfee that you had on your Windows XP computer ?
How did u purchase or Get your McAfee software ?
If you had registered then you can try to download the Compatible version of McAfee from your online account.