That doesn't sound like a private key... The only formats that I know of are:
Private Key WIF:51 characters base58, starts with a '5'
5HwVta1hpYkNRTRbJVEmiVEyKKV3ZVqY7Tmmn62udYqpjDrYsct
Private Key WIF Compressed:52 characters base58, starts with a 'K' or 'L'
KwmYWci7As8RYwdYQBdnN7efZranJSHEKXAce1DRJKYVfCtjFYVa
Private Key Hexadecimal Format (64 characters [0-9A-F]):10604F9F1D4DBB24EE7D1E07BFA649DC1539996D603B5A87109EAEA9F3F053C6
Private Key Base64 (44 characters):EGBPnx1NuyTufR4Hv6ZJ3BU5mW1gO1qHEJ6uqfPwU8Y=
Did you remember if you ever used a wallet called "Armory" at all? It *might* be an Armory "Root Key", although I think that should be 18 groups of 4 chars...