Windows 7 RTM or SP1 – Slow System Startup When Your Machine Contains a Large Hard Disk Drive

You may find that when you have a large hard disk drive the number of restore points that are retained causes the Windows 7 boot plan to exceed the file size of 512 kilobytes (KB).  512 KB being the precached limit means that the boot plan is no longer cached and causes the system startup to be slower. This is due to the fact that each restore point needs to be verified during system startup and as a result gets included in the boot plan.

A hotfix is available from Microsoft KB 2555428 that resolves the issue