http://bit.ly/sOwJ3G
Sorry, just a joke . Not seen a lmgtfy post for a while
It's intel's rapid storage technology http://www.intel.com/p/en_US/support/highlights/sftwr-prod/imsm
Was it definitely working before? I think it only applies if you're running hardware or software RAID.
EDIT: Further googling uncovered this: http://answers.microsoft.com/en-us/windows/forum/windows_vista-system/intel-rapid-storage-technology-service-is-not/7a269721-f4af-40de-b4d4-e72c5db9e988
Intel® Rapid Storage Technology (Intel® RST): With additional hard drives added, Intel® RST provides quicker access to digital photo, video, and data files on single-drive or multi-drive systems with RAID 0, 5, and 10, and greater data protection against a hard disk drive failure with RAID 1, 5, and 10. Support for external SATA (eSATA) enables the full SATA interface speed outside the chassis, up to 3 Gb/s.
I'm not exactly sure if it was working before but when i first time got this desktop, I havent see this icon until a week later.