Determine Who Are Putting Up Obstacles
The first step in trying to get this issue addressed is determining who are actively supporting you and who are putting up the obstacles. Lets take your line manager for example. Is your line manager starting the process and fighting against IT to get you the hardware you need, is the manager ignoring you or is indifferent, or is actively trying to not get you that PC since they do not want others also asking for a new PC (and the budget is not big enough to get everyone new PCs).
You will want to find people in IT or management who care about you, will work with you, and champion your cause and help defeat the people putting up obstacles. Ask them the questions like how to deal with the paper pushers, what worked and did not work in the past, and have them setting fires under those who need the push. If you are unable to find anyone like this then the best option is to polish your resume/CV and begin looking elsewhere, since the chance of getting this resolved will be extremely low.
If the situation is that your manager has dealt with IT so much over the years that they are simply exhausted from dealing with them and do not have the energy to help you, then this can be fixed. Try to motivate them to fight and do the right thing. Some small encouragement and affirmation that they can do it can go a long way to getting them to step up and fight for you.
Challenge the Process
They require you to do development inside of a VM. Is there a way to do development outside of the VM or is everything locked down outside of it? If you can do development outside of it, ask fellow developers if they follow the develop in a VM rule. You might find out that all the other developers have quietly been ignoring the rule, but have not told management/IT since they do not want IT coming in locking it down. Be warned this approach tends to fall under the policy of sometimes it is easier to ask for forgiveness then to ask for permission.
Bypass the Problem
Sometimes IT can be a penny wise and a pound foolish. If they are refusing the request because they do not have the budget to replace everyone's PC/laptop (and thus they wont replace anyone's PC/laptop since that would be unfair to the rest) then change the request so that it would not come from that budget. I have seen stories of how people have gotten a new top of the line machine, because they worded the request such that IT thought it was for marketing to demo the company's products. Marketing does not need powerful machines, but if customers are going to see it, then it must be the best even if it does not need to in order to reflect on the quality of the company.
Depending on the nature of the IT department and project you might be able to get creative with solving this issue. A situation happened to me where I had no development machine at all:
When I started on the program I had a company machine connected to the company's network, but I did not have a development machine connected to the development network. This was because IT rejected a request from my manager which they really should not have and they were refusing to address it. The company machine was too weak for development and locked down such that I could not do development on it. However, the development environment was reachable from the company network and they had a few windows server VMs on the development environment. So I proposed have a windows server VM spun up for my own development purpose. This bypassed IT since development team admins were responsible for managing VMs and so they started one up for me. So I ended up remoting into a windows server from the company machine to do software development and it worked surprisingly well.
So see if there is anyway specific to your company that you can bypass the problem and get a development environment that meets your needs (like a windows server VM where you remote into it).
Break the Problem
This can backfire thus I do not endorse this and do not recommend doing this, but for completion sake I am listing it.
Sometimes the fastest way to solve a problem is to break it more. How many people wait to fix a leaky pipe till it turns into a major problem? People have a tendency not to fix small issues until they become major issues. So in your case take your issue and make it an even bigger issue. Intentionally push the ultra-book to the point that when it freezes and locks up you cannot fix it and IT has to deal with it. If IT starts having to spend 4+ hours a day in your cubicle/office trying to fix the ultra-book for their own sanity they might get you a new one. This can back fire horribly since IT might get you an even worse/older machine to use, and it will directly cause your performance to drop, which can make people above you rather unhappy and there is no telling who they will direct it against.
Document Document Document
As said by others always document in email chains and other documents things that are actively hurting your performance and save them. These types of issues can go from getting no attention to people rather high up asking questions like why developers are missing deliverables? So no matter what path you take, having documentation to protect you is very important.