I was on a guitar tab site earlier today when the dreaded threat detected dialog popped up from security essentials. It said it was removing the threat but needed to restart...which it then did. Now after booting up the box runs for about three minutes...then tells me a threat has been detected and removed and then does the restart thing again. I can't run a scan because the box keeps rebooting itself. Any suggestions will be greatly appreciated.

Can you start in safe mode and run the scan?

What James said.  Usually the key to hit while booting up is F5 (you should get something that tells you what to hit).  Then select Safe Mode and run the scan there.

And/or try to restore to an earlier point after safe boot?

Turns out these two are doozies...Sirefef.Y and Sirefef.B

Bad mamma jammas. I've tried several web solutions to no avail.  Dang!

try major geeks or hijack this.  they have cures fer what ails you my ol pal.

http://www.microsoft.com/security/scanner/en-us/default.aspx

which guitar tab site were you on? 

guitar tab porn? 

LOL Beagle! I know your company security is as mine...I got blocked
from a legit site called "Sexy Guitars".

Would that it were so but no...it was a guitar tab site of all things.  And it will definitely be a trip to the computer guys tomorrow.  I tried most every solution proffered on the world wid yawn.  But this thing's tenacious.