Do a google search for acpi.sys or acpi.sys corrupted and you will find a lot of info on it. 

A Windows XP "Repair" procedure will probably fix it too, but you will need a Windows XP install CD to do that.

Hi Emma

 

Dell model code doesn’t mean much in these Forums, better if you include the Dell model (e.g. Inspiron, etc.)

 

Also helps if you can provide information about anything done just before the problem started?

E.g. hardware added/changed, was computer shutdown normally (Windows shutdown) or not, etc…?

 

If hardware or BIOS is causing the problem then a Dell OEM XP CD won’t help?

 

Otherwise if software related, you will need to obtain a Dell OEM XP Pro CD, as mentioned by fireberd

Note: you can’t use an XP Pro SP2 version CD for repair if the present OS is XP Pro SP3

 

Anyhow, if in the USA, then click here to request Dell CDs

If not then you need to contact your local region Dell Support

 

Otherwise you could restore computer to factory condition by initiating Dell PC Restore

Dell step-by-step procedure is click here

Note: if you use Dell PC Restore, you will lose All your personal data & any software added since purchase date