As most of you probably experienced, NetFX 3.5SP1 offers significant performance improvements over NetFX 3.5.However, we received some reports where NetFX 3.5SP1 installs are seen to be making some select few applications startup slower than they were in NetFX 3.5, whereas for most applications startup performance improves significantly with NetFX 3.5SP1.

The possible reason for this anomaly is because the installed images are being dispersed into many fragmented pages in a fragmented volume, thereby increasing disk i/o during start up. This issue can be fixed very easily by doing a full defragmentation of your hard drive.

Note that in Windows Vista, it automatically defrags your disk at scheduled intervals, thereby resolving the issue over the course of time.  Similarly, on WindowXP the operating system will defragment files that are used at startup of an application within 3 days of their use to optimize their cold startup.  

However, if one wishes to maximize performance immediately following a NetFX 3.5SP1 install, a defrag is suggested.

To defrag your harddrive in Vista, select Start --> All Programs --> Accessories --> System Tools --> Disk Defragmenter --> Defragment now.

In Windows XP, select Start->Programs->Accessories->System Tools->Disk Defragmenter --> Defragment.