Can you get SQL Server Manager Studio going. In the tree, under your server, unser system databases, you should be able to see (usually) at least Master, Tempdb, Model and MSDB. I suspect tempdb will be marked are broken or possibly recovering or some such.
The default installation would create two files tempdb.mdf and templog.ldf, on teh install path, should also be two files for each of the other system databases in teh same place.
Path would be something like C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\DATA
If these files have 'erm disappeared and you can get them back, this would be good.
To see where sql server thinks they are if management studio runs, right click on tempdb in the tree, select properties, select the files tab, scroll across.
If tempdb isn't in the tree, but the files exist then you might get away with, sttchimg them. Right click on databases in the tree (tree node parent of system databases) select attach browse to the files)
If you get some mnore clues from sql management studio, you'll have to shout back, as I never seen this fault.
Worst comes to the worse.
You can restore the server, restore the database, if you've done a full back up of master (and all your other stuff). Short of that you can rebuild the master database, which is f'ing painful, or simply unistall and reinstall which might be easier.
NB, if you do either of the latter two you will of course go back to day one, lose all config changes your databases etc. So for Cthulu's sake back them up before you do any of that. SQl server back up of each (not master !) one. and may be even last ditch. stop the server and copy the phyical files.
It's real hard to advise of this one blind, if the data is critical and you aren't sure of what you are doing, I recomend you get a professional on site.
If it's a doesn't matter, persopnally I'd go for clean install.
NB To rebuild the master database, you need the original install disc (well same version e.g. SQL Server 2005 Workgroup). And you'll have to re do all the service packs, patches etc anyway, as it will go back to whatever was on cd.
Seriously if this is a meaningful box get a pro on site, it might cost you a couple of hours, but you don't want to get this wrong.
Either way have a good lok before you leap. I'm meant to know waht I'm doing and I had two test runs at rebuilding master database. I'll see if I can find the procedure tomorrow, if I can I'll tidy up and post. NB I was rebuilding master for a completely different reason, but it should basically be a goer.
If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem. Also please exercise your best judgment when posting in the forums--revealing personal information such as your e-mail address, telephone number, and address is not recommended.
Event id SQL SERVER
Error: 615, Severity: 21, State: 1
Could not find database table ID 2, name 'tempdb'.