Well the advantage to 64-bit is that it can run 64-bit as well as 32-bit programs and it can reference beyond 3.25GB of RAM (so if you have 4GB it will see/use all of it). 2GB is the minimum RAM recommended for 64-bit.
You can back up your userids (logon ids) and settings and any data you've created using WET (Windows Easy Transfer) which is built into W7 (use the advanced settings to make sure you get all your data. Back these up to DVD or external HD/flash drive.
You should also spend some time on the manufacturers site downloading 64-bit drivers for your computer and burn those to CD/DVD or put on a flash drive.
Now about installing 64, first off I would check to see if your harddrive has a restore partition. It sounds like it originally gave you a choice when you turned it on day 1 and if those files are still there you may be able to format the W7 partition and restart from the restore partition. I'm not sure exactly how you would do this - since it is a new machine you are entitled to support so contact the manufacturer.
OTHERWISE, You can download and burn W7 Pro x64 using
the official links. Note: while on the manufacturers site, download any special programs they include because the official W7 will not have vendor supplied programs. This may include programs to use special function keys on the keyboard and things such as on-screen volume display.
Do a format and install using the drivers disk as needed. Restore the UserID Logons/settings/data from the WET back-up. Reinstall all your programs.
