If you never had CD's either there is a recovery partition / application on the hard drive or there are installation CD images ready to burn on the hard drive - legally some method of recovery must have been supplied.
In any case so long as you have the XP label with the 25 character key and it is readable you can re-install with any unbranded XP home CD of the same level e.g. with SP1, SP2, SP3.
If originally SP1 or SP2 any CD that is not SP3 will probably accept the key.
Ask around - if you get stuck I have a couple I have used to get people out of trouble but need to check versions.
You will also need to download your drivers and antivirus software (eg avast) and firewall (eg Comodo) and store on a CD or USB memory (virus free of course) before you start.
I have met this print spooler issue as a result of a virus, I recall a repair patch exists but a good chance you have other corruption too.
After 5-6 years a re-install is a good idea anyway.
As others have posted at best Windows 7 on a 5-6 year old PC will be disappointing.