Expenses incurred

Yes, you can claim that PC purchase as an expense! It doesn't matter which account you paid from, whether it was your personal account, another business account or even cash.

The most important thing is that you have the invoice as proof. As long as the document states sufficient details about what you bought and how much it cost, you can perfectly record that expense.

As extra information: if you are a sole proprietor, you can freely transfer money between your various accounts. The payment does not play a role, whether it is from bank account X or Y. You just need to be able to prove that you have paid.