Since you have a Dell computer, I would first check with their support. You said you have no installation disk, but maybe it is still there in your hard drive in a hidden partition. They should know how to guide you for your specific model and configuration, which you haven't comment here anything about.
In any case, you have to know that using a hidden partition to reset you hard disk, or installing a again any Windows OS, would probably make your previous saved information (personal data / documents) even more dificult to retrieve. Since you didn't mention anything about it, maybe this is an unknown issue for you. If you haven't any info to recover, then go ahead. If you have info to recover, you should use recovery programs (from UBCD, for example) and save it in some external device (not in the same hard disk partition).
About checking the BIOS, I think (I may be wrong) the suggestion was to actually get into your computer bios, not to use first UBCD.
Google "how to get into BIOS". Even more, Dell support web pages might give you the answer how to do this in your particular model. Look for the online manual.
Once you get into the bios options, look around and take note for every info displayed about your hard drive configuration, and also look for the boot option / boot order.
According to your hard drive manufacturer, there might be tools to check it for errors. Again, Dell support should help you about the relevant info.
If this type of tool states that there is no terrible problem with your hard drive, then maybe, just maybe, you don't need to reinstall the OS, but just find the right tool to "unformat" or maybe to recover some partition information, and your hard disk would return to be bootable without problems and with all your previous info in it. This is a long shot, since you said you ran a wipe tool over the disk.
You did not mention anything about when the boot problem started. Is there anything you did or anything ne happening when the boot problem started? Whis is the reason you decided to wipe your disk? What you were trying to accomplish?
About installing another OS instead of Vista, if you get to the point there is no other better option than to install a new OS, then you can install anything you want, if you legally have the correspondent keys, or even a free OS.
The advantage of reinstalling the same OS you had before is less problems identifying info, partition boundaries which have rules-changes between XP, Vista and even for Seven, and that you already have a legal copy of it. If your Dell has also a hidden partition to recover the initial OS, then this is the more direct option to get to a clean point and a working computer.
Although all these steps and info may seem too much, I hope at least this points you to the right direction.