At this point whichever OS you start up will likely cut the other one out of the Dual Boot, but it can be added back using EasyBCD 2.0 beta.
You can boot free Partition Wizard bootable CD
, copy down what the labeling now on all partitions and post back.
What I would do is mark Windows 7 active using PW, boot into the Windows 7 DVD Repair console or Repair CD, click through to Recovery Tools list to run Startup Repair up to 3 times with reboots, when it starts install EasyBCD 2.0 to Add Vista to Dual Boot Menu.
You can do the same with Vista using its DVD Repair console/Repair CD , but it needs to be marked Active first with PW CD. Best to post back the details shown on PW drive map so we can give you the exact steps.