There was a recent trial on MS, aspirin, and fatigue. It was a placebo-controlled, randomized cross-over double-blinded trial, which is good design and especially needed for something subjective like fatigue. It was a small study (N=30), but with randomized crossover design you don't need as many subjects. Aspirin helped with fatigue in this study. Here is abstract, there is a comment in the same journal but I can't view that:
Neurology. 2005 Apr 12;64(7):1267-9. Related Articles, Links
Neurology. 2005 Apr 12;64(7):1111-2.
A randomized controlled crossover trial of aspirin for fatigue in multiple sclerosis.
Wingerchuk DM, Benarroch EE, O'Brien PC, Keegan BM, Lucchinetti CF, Noseworthy JH, Weinshenker BG, Rodriguez M.
Department of Neurology Mayo Clinic, Scottsdale, AZ 85259, USA. firstname.lastname@example.org
Pharmacotherapeutic options for multiple sclerosis (MS)-related fatigue are limited. Thirty patients were randomly assigned to aspirin (ASA) 1,300 mg/day or placebo in a double-blind crossover study. Results favored ASA for the main clinical outcomes: Modified Fatigue Impact Scale scores (p = 0.043) and treatment preference (p = 0.012). There were no significant adverse effects. The results warrant further study and support a role for ASA-influenced mechanisms, perhaps immunologic, in the generation of MS-related chronic fatigue.
Randomized Controlled Trial
PMID: 15824361 [PubMed - indexed for MEDLINE]
I couldn't find any other study that had an abstract, there were two trials from the early 1960s - those may have been what jimmylegs mentioned. Well, if aspirin doesn't help the overall disease course, at least this study indicates it may provide some fatigue relief.