How many bug fixes are included in Windows Vista Service Pack 1? By Microsoft’s count, SP1 rolls up 551 separate hotfixes, in addition to 23 security updates rated Important and already delivered via Windows Update. A handful of those hotfixes were previously released via Windows Update, but most were available only to corporate customers and OEMs. If that sounds like a lot, well, it is. But it’s not out of line with the number of fixes that went into the first two service packs for Windows XP. I've got the full breakdown by category.