You have three problems that are quite evident, two related to the junk PSU and one to low free storage space on the C: drive, the latter will not have been the cause of the annoying blinking but if not addressed it will result in a corrupt OS and/or a failed HDD.
To the PSU, where do I start, the following in no particular order and all equally as important, the PSU is badged as 500W but when tested could not even produce a stable 400W, it was so bad in fact that the testers Hardware Secrets recommended Thermaltake rebadge the unit as 300W, see report here pay particular attention to what is said about the amps that the unit produced;
Being able to get only 375 W from a 500 W power supply is not the worst part: starting at 310 W +12 V outputs were presenting voltages lower than the minimum allowed, offering real risk to your components.
The Thermaltake Purepower W0100RU was first released way back in 2008 meaning that your PSU has the potential to be 8+ years old, the said unit was tested by HW S in 2010 so even allowing for this the present PSU would be out of warranty and even if a good PSU it should have been replaced before now in any event and with a minimum of a 500W bronze rated unit from a reputable company.
Speccy is showing that the output on the +5 and +12V rails on the PSU is too high, your computer is not under any load at present and these figures will change when it is and not for the better.
Your video card requires a minimum of a 450W PSU with 34 amps on the +12V rail, the present PSU cannot produce either, never has and has quite possibly caused irrepairable damage to one or more of the other hardware components. Radeon HD 5770 1024MB PSU requirements info here
Your CPU is showing the Average Temperature: 71 °C this is not only way too hot for a processor that is doing next to nothing but also the max before the CPUs thermal trip should activate and shut down the computer, CPU specs here
the temps are most likely the cause of the bad PSU as it struggles to produce the power required but would recommend that the inside of the case be checked for dust build up around the HS and CPU cooling fan and to see what other cooling fans (if any) are present etc.
I strongly recommend that you do not use the computer until the present PSU has been replaced, an example of the PSU that you need here