I have the solution having just been dealing with this for the last two hours and thought I'd let you know how I fixed it.
As it turns out, my constant re-installations of Times New Roman (and Arial) weren't changing anything because I'd run the Vista Font Fix from here:
Fix Windows Vista’s Fonts! ~ Chris Pirillo which actually changes the font types in the registery, associating them all with the Segoe UI font file and thereby totally ignoring the Arial and TNR files you're reinstalling.
Your registry should probably look like this (taken from here:
Reverse Vista Font Fix - Vista Horizons):
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontSubstitutes]
"MS Shell Dlg 2"="Tahoma"
"MS Shell Dlg"="Microsoft Sans Serif"
"Helv"="MS Sans Serif"
"MS Sans Serif 8,10,12,14,18,24"="MS Sans Serif 8,10,12,14,18,24"
"MS Serif 8,10,12,14,18,24"="MS Serif 8,10,12,14,18,24"
"MS Sans Serif"="MS Sans Serif"
"System"="System"
"Microsoft Sans Serif"="Microsoft Sans Serif"
"Tahoma"="Tahoma"
"MS Serif"="MS Serif"
"Times New Roman"="Times New Roman"
"Times"="Times"
"Small Fonts"="Small Fonts"
"Tms Rmn"="MS Serif"
"Arial"="Arial"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts]
"Arial (TrueType)"="arial.ttf"
"Arial Italic (TrueType)"="ariali.ttf"
"Arial Bold (TrueType)"="arialbd.ttf"
"Arial Bold Italic (TrueType)"="arialbi.ttf"
"Times New Roman (TrueType)"="times.ttf"
"Times New Roman Italic (TrueType)"="timesi.ttf"
"Times New Roman Bold (TrueType)"="timesbd.ttf"
"Times New Roman Bold Italic (TrueType)"="timesbi.ttf"
"Tahoma (TrueType)"="tahoma.ttf"
"Tahoma Bold (TrueType)"="tahomabd.ttf"
"Microsoft Sans Serif (TrueType)"="micross.ttf"
"MS Serif 8,10,12,14,18,24"="SERIFE.FON"
"MS Sans Serif 8,10,12,14,18,24"="SSERIFE.FON"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontMapper\FamilyDefaults]
"Swiss"="Arial"
"Roman"="Times New Roman"
Once this is done, everything will either look fine or you'll have the horrible situation of both Arial and TNR being bold and/or italic in odd places and looking wrong. To then fix this, I searched the Windows directory firstly for "Arial" and then for "Times", finding files in the folder
C:\WINDOWS\WINSXS. I installed the fonts, overwriting the existing files and all is working perfectly.
I'm unlikely to think to come back to this thread so if there are any associated problems from following the above, please email me and I'll then return here to continue troubleshooting.
*Note that I used System Restore to return to a point prior to running the Vista Font Fix though the above should work absolutely fine.