SP may refer to any of the following:
1. Short for service pack, an SP is a large update containing several fixes and updates for Microsoft Windows operating systems. Service Packs are a collection of fixes that help resolve software and hardware related issues with Microsoft Windows. It is highly recommended that all Microsoft Windows be running under the latest Windows Service Pack. Below are the different Service Packs available for each of the major versions of Microsoft Windows.
Microsoft Windows Vista - SP1 and SP2
Microsoft Windows XP - SP1, SP2, SP2b, SP2c, and SP3
Microsoft Windows 2000 - SP1, SP2, SP3, and SP4
Microsoft Windows NT 4.0 - SP1, SP2, SP3, SP4, SP5, and 6.0a.
2. Abbreviation for spelling, SP is often used in online communications such as chat where you're typing a word and not sure on the spelling. Below is an example of how this could be used.
User1: So did you see that guy last night?
User2: I sure did, it was fun.
User1: What's his name?
User2: It's Abraham (sp?)