Soldato
If it's a 15 year old carpet, it's probably quite manky. You're probably only liable to remedy things to the state they were in. Therefore either cleaning or replacement with an equally manky aged carpet. Depending on what carpet it is, it might be bleach cleanable unless it's real wool. If it's oil,.not sure how oil gets on the underneath of a pc but maybe some mechanics hand cleaner will shift it. Obviously, you'd then need to clean the swarfega or similar off. It can't be a very big mark unless the case was full of crude oil!
Always read the label and test in an unnoticeable area first. Just saying so I don't end up liable for a new carpet.
Always read the label and test in an unnoticeable area first. Just saying so I don't end up liable for a new carpet.