I'm assuming it's Vista?
Wheels, don't know how savvy you are, but I agree with the comments about PC World. You need a Whizkid to have a look at it properly before you write it off - No disrespect to yourself of course.
A lot of manufacturers don't really give you good restore disks or a copy of Windows.
I would try resetting the MBR, or doing a Sys Restore.. Do some research
Go to this site - and read, read, read
http://www.pcbuyerbeware.co.uk/Recovering_Repairing_Windows_Vista.htm#intro
More tips here:-
http://www.pcbuyerbeware.co.uk/Recovering_Repairing_Windows_Vista.htm
Then get the discs mentioned here:-
How to create a WinRE disc if your OEM computer came with a Recovery Disc instead of a Windows Vista installation DVD
If you have an Windows Vista computer (desktop or laptop) made by one of the major manufacturers (Dell, Acer, HP, Toshiba, Lenovo, etc.), it will have come with its manufacturer's recovery disc that resets the system to the state it was in when it left the factory, not a Windows Vista installation DVD. You need a real Windows Vista installation disc in order to be able to access the Windows Recovery Environment (WinRE) that Vista's Startup Repair uses, so you won't be able to use it. However, the following website provides a valid boot disc that runs WinRE.
Windows Vista Recovery Disc Download -
http://neosmart.net/blog/2008/windows-vista-recovery-disc-download/
Download: Windows Vista x64 Recovery Disc -
http://neosmart.net/blog/2008/download-windows-vista-x64-recovery-disc/
The second link provides a download for the 64-bit versions of Windows Vista and provides information on how to download and use .torrent files.
The files are ISO files that have to be burned as disc images not as data files. Most disc-burning software provides an option to burn a file as an image.
It is a safe website. The comments provided by readers may prove to be useful. After downloading the image to your a folder on your Vista computer, create a CD in ISO format. You can use a recordable CD disc; a recordable DVD disc is not required as the ISO file is only 120MB. On the CD/DVD, there are two folders Boot (3.27MB), Sources (116MB) and one file Bootmgr (325KB). It works in the same way as a Vista installation DVD. Just boot from the disc, (your computer's BIOS will have to be entered at system startup prior to Windows startup by pressing its entry key in order to set with the CD/DVD drive as the first boot device if it doesn't boot from the disc automatically), choose Press any key to boot from CD/DVD and Vista will start to load the Windows files. Select your language, time, currency and keyboard then click Repair in the bottom left corner. Within the Repair option there are five choices: Startup Repair, System Restore, Backup Restore, Memory Test and Command Prompt.
If you have made a backup using any ofthe backup options in the Windows [Vista] Backup and Restore Center, you can use the Backup Restore feature on the dsic to restore the backup. Making a backup of the whole system is the best way of protecting your computer from irrecoverable software failures.
Then have a look here:-
http://support.microsoft.com/kb/927392/en-us
You do the bootrec.exe /fixmbr, then /fixboot first, then move onto /scanos, then if all else fails then you do a total rebuild /rebuildbcd
But before you do you export the old BCD just in case this is the process:-
Note If rebuilding the BCD does not resolve the startup issue, you can export and delete the BCD, and then run this option again. By doing this, you make sure that the BCD is completely rebuilt. To do this, type the following commands at the Windows RE command prompt:
bcdedit /export C:\BCD_Backup
c:
cd boot
attrib bcd -s -h -r
ren c:\boot\bcd bcd.old
bootrec /RebuildBcd
Best of luck!