Cisco 1721 Router Problems

I have a Cisco 1721 router that is stuck in rommon. I have two IOSs that i’m trying to upload onto the router using xmodem but it keeps telling a ‘process cancelled by remote host’ message then
‘ERR: File not a valid executable’ message in hyperterminal. This happens with both images What am i doing wrong?

IOS names:
c1700-y-mz.123-5.bin,
c1700-bk9no3r2sy7-mz.123-3

ps. im using a cisco pdf lab on managing IOS images in rommon.