Yes it is.
It's the past tense of "spell".
It doesn't even get underlined in red in this here text box I'm typing in. Spelt.
( Moon Girl Technologies horrendous beanbag, Mon 13 Aug 2007, 18:00, archived)

wouldn't that be "spelled"?
It's sure underlined in my text box. Spelt.
( J-Rod chortled as he came, Mon 13 Aug 2007, 18:04, archived)

Is your dictionary set to 'US'?

( Moon Girl Technologies horrendous beanbag, Mon 13 Aug 2007, 18:05, archived)

I'm guessing it might be set to 'fuckwit'

( Amorous Badger NAKED BEA ARTHUR PHOTOS 4U, Mon 13 Aug 2007, 18:06, archived)

aren't they the same?

( J-Rod chortled as he came, Mon 13 Aug 2007, 18:08, archived)

now now
this is just unnecessary.
( Moon Girl Technologies horrendous beanbag, Mon 13 Aug 2007, 18:08, archived)

Now look.
If people stop being fuckwits, I'll stop mocking them.
( Amorous Badger NAKED BEA ARTHUR PHOTOS 4U, Mon 13 Aug 2007, 18:09, archived)

He wasn't being a fuckwit.
He told a dull OMGDRUGS story and didn't know that British English allows 'spelt'.

Not a fantastic contribution to the afternoon's entertainment, but not really fuckwittery either.
( Dr. Shambolic je suis charlie, Mon 13 Aug 2007, 18:12, archived)

I think badger has had a bit too much orange squash and is getting over-excited.

( Dr. Shambolic je suis charlie, Mon 13 Aug 2007, 18:10, archived)

Kia-Ora used to send me funny as well.

( Moon Girl Technologies horrendous beanbag, Mon 13 Aug 2007, 18:12, archived)