Start here: repair or replace? How to decide in 5 minutes
Before you spend money, answer three questions.
1. How old is it? A computer under 5 years old is almost always worth fixing. Over 7 years, compare the repair price with a new machine first.
2. What's actually wrong? Slow, pop-ups, won't start and cracked screens are usually affordable fixes. A dead motherboard on an old laptop often isn't worth it.
3. Is your data safe? If the computer has photos or work files you can't lose, protect those first, whatever you decide.
The cheapest fixes that make old computers feel new: swapping the hard drive for an SSD, a proper virus and junk cleanup, and more memory.
Post your problem in this topic with the make, model and what happens when you turn it on, and I'll tell you honestly whether it's worth fixing.