How to find the level of SharePoint you are running

Using SharePoint Central Administration Web site SharePoint HTML Site Settings admin pages or IIS Manager, on the web sites properties HTTP Headers tab, virtual servers once extended will show the following version numbers:
MOSS 2007¹ or WSS 3.0 Cumulative update (KB956056 & KB956057) 12.0.0.6327
MOSS 2007¹ or WSS 3.0 Infrastructure Update (KB951695 & KB951297) 12.0.0.6318
MOSS 2007¹ or WSS 3.0 post-SP1 hotfix (KB948945) 12.0.0.6303
MOSS 2007¹ or WSS 3.0 post-SP1 hotfix (KB941274) 12.0.0.6301
MOSS 2007¹ or WSS 3.0 post-SP1 hotfix (KB941422) 12.0.0.6300
MOSS 2007¹ or WSS 3.0 SP1 12.0.0.6219
MOSS 2007¹ or WSS 3.0 October public update 12.0.0.6039
MOSS 2007¹ or WSS 3.0 August 24, 2007 hotfix package 12.0.0.6036
MOSS 2007¹ or WSS 3.0 RTM 12.0.0.4518
MOSS 2007¹ or WSS 3.0 Beta 2 TR: 12.0.0.4407
MOSS 2007¹ or WSS 3.0 Beta 2: 12.0.0.4017
Office 12 (PDC image - pre-beta): 12.0.0.3111 (This version of Office does not have a support link in the Add/Remove programs dialog box).

¹To confirm that a particular service pack is install on SharePoint Server you must either check the version numbers of specific dlls as specified in the related Microsoft Knowledge Based article or select the Show Updates check box in Add and Remove Programs.

WSS 2.0 SP3 6.0.2.8165
WSS 2.0 SP2 KB900929 + KB924881 6.0.2.8117
WSS 2.0 SP2 rollup KB900929 6.0.2.8000
WSS 2.0 SP2 6.0.2.6568
WSS 2.0 SP2 Beta = R2: 6.0.2.6551
WSS 2.0 SP1 + KB887981 6.0.2.6411
WSS 2.0 SP1: 6.0.2.6361
WSS 2.0 Unservice packed: 6.0.2.5530

To confirm that service packs are installed, especially with SharePoint Server 2007, goto Control Panel -> Add and Remove Programs
Select the product and then click: Click here for support. The versions will
be displayed as follows:

	Windows SharePoint Services 3.0	Microsoft Office SharePoint Server 2007
post-SP1 hotfix (KB948945)	12.0.6303.5000	12.0.6303.5000
SP1	12.0.6219.1000	12.0.6219.1000
RTM	12.0.4518.1016	12.0.4518.1016
Beta 2 TR	12.0.4407.1005	12.0.4407.1005
Beta 2	12.0.4017.1006	12.0.4017.1006

	Windows SharePoint Services 2	SharePoint Portal Server 2003
SP3	11.0.8173.0	11.0.8168.0
post SP2 rollup	11.0.8000.0	11.0.8126.2
SP2	11.0.7969.0	11.0.8126.0
R2 WSS SP2 beta	11.0.6551.0
SP1+KB887981	11.0.6411.0
With Service Pack 1	11.0.6361.0	11.0.6715.0
Unserviced pack	11.0.5608.0	11.0.5704.0