First try a system restore. Boot your computer up and when you see the BIOS splash or whatever comes up first on your PC spam the fuck out of F8. Select boot from safe mode and read everything and proceed to the system restore utility. If you are unable to boot into safemode, simply go to a local computer repair store, or call around. Most of them are friendly enough to let you have a vista or XP install disk.
Also your laptop might have whats called a recovery partition. If that is the case you do not need a disk to reinstall your OS. Although I've never had much luck with the restore partitions it is worth a shot and its free.
As for backing up your data, hope your hard drive is SATA and find someone with a newer computer, if it is IDE you will need an adapter for an 2.5" hdd that has a molex power adapter as well as the 40 Pin adapter for the data cable, these cost about $15. Get a spare SATA data cable and hook your shit up to his/her computer and back up all your stuff. SATA drives are hotswapable so you really do not even have to turn your friend's PC off before you connect it. Your data should show up just like a regular hdd or external. Its a piece of cake.
Also downloading a disk or borrowing one from someone is completely legal so far as you use the license on the bottom of your laptop. ALL OEM DISKS ARE GENERIC AND CAN BE REUSED BY ANYBODY. DO NOT BE AFRAID OF BORROWING SOMEONES DISK. Also, all OEM version disks that have vista usually contain every version of vista and the features relative to your version will be activated by your specific product key. AGAIN DO NOT BE AFRAID OF USING A FRIENDS DISK AS LONG AS IT IS AN OEM COPY. DO NOT TRY TO USE A RESTORE DISK FOR A DIFFERENT TYPE OF COMPUTER, YOUR SHIT WILL NOT WORK.
Most importantly DO NOT TAKE YOUR COMPUTER TO BEST BUY. YOU WILL REGRET IT.